Seasonal Anime Marathon — Spring 2021 edition

Daniel Kihlgren Kallander
15 min readApr 25, 2021


Me at the start of every new Seasonal Anime Marathon (source unknown)

(If you’re just here for the summaries, feel free to skip the first section below)

“How do we know which shows are worth watching each anime season?”

That’s the question me and some friends were asking ourselves as we realized that - despite spending a lot of time watching anime together - we were missing out on several great shows each new season. Most of us are in our late 20s to early 30s, live normal busy lives, and didn’t really feel like we had time to apply the normal “3 episode rule” to each show as a lot of shows would just be painful to have to sit through for that long.

We had already been doing several lengthy movie- and anime marathons together around some themes, and we realized that if we cut off any series that requires prerequisite knowledge (continuing shows, closely linked spinoffs, etc) and just focused on the first episode of each original new show, we would end up with a solid 10-to-12-hour marathon each season — a length not far off from something like a LotR Extended Edition marathon.

Thus, our Seasonal Anime Marathon was born, and somewhere along the way I started doing a one-tweet-per-show summary after each event. In part just to remind myself of what we saw, but also so anyone not having time to join the entire marathon would be able to read what the rest of us thought of any certain show. After having done that for about two years now, I’ve realized I often have more than 280 characters worth to say about most shows, so I’m moving the summary to this long-format article instead.

We’ll see if this version sticks around, but comment below or let me know over at if you found this useful! Now, that’s enough backstory, on to the actual shows for Spring 2021!

Out of the 34 in total, there are A LOT of great ones this season! We watched these in 13½ hours, I then had less than 4 hours of sleep, and now I’m writing this, so forgive me for forgetting names etc!

As always, the order these are listed in is simply the order we watched them.

Tokyo Revengers

Guy in late twenties is feeling sad about his stale state of life as he learns that his high-school girlfriend and her family was murdered. Shortly thereafter, he gets into an accident that activates an ability to travel back in time to change the past.

Didn’t really manage to grab any of us, but has potential? A lot of comparisons to ‘Erased’, but I haven’t seen that show yet so I can’t comment on in what ways it’s similar.

Cestvs: The Roman Fighter

Before the marathon I’d seen a lot of hate about the egregious 3DGC. Turns out it’s only at the start and end of the episode for some reason, and non-existent throughout most of the actual show? Still felt like nothing more than a very clunky ‘Hajime no Ippo’ wannabe.

Battle Athletess Daiundoukai ReSTART!

Potato-farm-girl finds crash-landed alien girl in the farmlands as a kid, but doesn’t make it back with help before alien girl disappears. From that she’s motivated to later join what seems like the solar-system-olympics in outer space? Also all that farm-work has made main-char-chan super strong, obviously. “Some” fan service shots and overall weird pacing, but if you enjoy hot garbage then it might be garbage worth keeping an eye on.

Dragon Goes House-Hunting

I’m not sure why, but I had some hope for this series going into it…

Seems like an OK fantasy comedy, but not more. The title is the premise of the show: main char (a young boy dragon) gets disowned and kicked out for not being dragon-y and strong enough. Now he needs to find his own place, and after some unsuccessful attempts to move in with Harpies and Goblins, he eventually finds an Elf that specializes in architecture and real-estate. RPG world with modern society mannerisms and house-hunting customs for enemy monsters => comedy is essentially what it’s trying to do overall. Lots of nods to RPG franchises like Monster Hunter etc.

The World Ends With You The Animation

Fully 3DGC animated show based on the story of a 2007 Nintendo DS game with the same name. While the game is beloved and the 3DGC was mostly excellent, the show’s first episode felt very much like a game story with the gameplay missing, which made the pacing feel off. Especially the fight scenes “looked like they were easy wins, there’s no sense of danger or real struggle”, as put by a friend. Overall sentiment was that people felt more inclined to go back and replay the game rather than continue watching this.

Super Cub

Here we go. First collective Yeah we’re definitely going to continue with this of the marathon. Super chill and wholesome, even if it’s essentially a feature-length Honda ad. The use of saturation to depict main-char-chan’s mood is fantastic. If you enjoy relaxing shows, this is a must-see.

I’ve Been Killing Slimes for 300 Years and Maxed Out My Level

Typical light-novel-lengthed title aside, this seems cute and watchable. Your average OP protagonist Isekai premise, but main-char-chan just wants to relax and spends her first 300 years (which gets very casually time-skipped) fighting 25 slimes per day for exercise which maxes out her level without her noticing. Word gets out that “The Strongest Witch” exsist, and her leisurely days now seem over.

I’ll be continuing to watch this, seems cute.

Jouran: The Princess of Snow and Blood

1930’s alternate history Japan, where the Shogunate was never abolished and the Emperor Meiji was never restored. Also there are supernatural beings and magical energy now.

Hard to properly place it after the first episode — it has potential but among other things that stood out (in a bad way), it has several characters that don’t look like they were meant to be in the same frame or show. Tries to be very edgy and dark. Underground assassin bases and monster hunters. A maybe for some of us, whereas in another season it might’ve been worth keeping up with for more.

Shaman King (2021)

Shaman King remake, meant to be more true to the manga than the original early 00’s anime adaptation. It’s a hyped Shounen Jump series, WYSIWYG. Seems like it’ll hold up. Most of us will continue watching.

Odd Taxi

Wow this is very different and weird and we love it. Modern crime/mystery story with plenty of character, depicted with an anthropomorphic cast. Main-walrus-ossan is bae. A must-see.


Military drama set in a heavily segregated sci-fi fantasy world. Main-char-chan is the only “Handler” that cares about the “dolls” (aka “the 86”) who pilot the spider mechs society sends to war. After an event, main-char-chan is reassigned to take charge of the infamous Spearhead division, whose previous Handlers all have either quit, gone insane, or taken their own lives.

Highly scored, but it will take more than the first episode to really hook us. Great production quality throughout and a lot of potential though, so one to at least keep an eye on.

Vivy: Fluorite Eye’s Song

Speaking of great production quality — WOW. Brutal opening where AI is killing humanity, and with his last breath a researcher sends his own AI back through time to try to prevent it from ever happening. The key to solving this lies with Vivy, the ‘first autonomous AI’, whose sole mission is to make people smile through her singing.

A Wit Studio production, with writing by creator of ReZero. Fantastic although brutal visuals. Plenty of AI uprising and dilemmas. We’ll definitely continue to watch this.

Blue Reflection Ray

The start of a minor “Trash Block” during our marathon. …at least that’s what we thought it would be.

All-female cast? Some mysterious rings that lets people see some shared memory? Magical girls?? Our collective sentiment was that we thought that this would be way worse than it actually was, and by the end of it we almost wanted to keep watching to see what happens.


Fairy Ranmaru: Anata no Kokoro Otasuke Shimasu

5 fairies are sent to Earth to collect “Attachment” for their (lolita) Queen. They have 10 commandments that all essentially boil down to “don’t get romantically involved with women”, and each fairy has a alter-ego they can turn into through a fantastic transformation sequence with it’s own full song. Do you ever find yourself thinking that it is weird that only women get very detailed and up-close transformation sequences? (it is)
Well here you go — these men have you covered for an alternative!

Beyond that, this is the show with the lowest score of the marathon, for good reason.

Good-bye, Cramer

We still don’t know who or what Cramer is, but this soccer anime was way more interesting that its score of 6.05 lets on. First episode has some endearing character moments and we’re looking forward to seeing more of the cast.

I don’t usually follow sports shows, but even I might stick with this for at least a few more episodes.

Seven Knights Revolution: The Hero’s Successor

Gatcha game adaptation with surprising production quality and some cool action sequences, but not enough of a hook for the overall world or story in this first episode to know if it’s something to keep watching or not. Very “Bland out of 10".

Let’s Make a Mug Too

This was precious. Slightly shorter at 15 minutes per episode, and we loved it. Fantastic visuals. Cute girls doing pottery things.

Edens Zero

Definitely not “Fairy Tail in Space”. Nuh-uh.

I’m caught up with the manga so I already know where the story goes, but the first episode is worth taking a look at to see if its your cup of tea or not. (Stick with it to the end of the episode if you do give it a shot)

Visuals-wise it’s your typical shounen battle anime type production quality. Nothing great like Jujustu Kaisen, but not bad. If you’ve seen Fairy Tail you know what to expect.

Lots of fan service.

Mars Red

In one word: Cinematic.

1920’s Japan but there are vampires, and the military is tasked with keeping them secret and at bay. Some of the best stills of the marathon. Some scenes reminded me more of western shows like True Detective more than any anime.

I’m continuing this even if only for the visuals, and the story might be decent as well.

just look at this shot, ffs. (Mars Red)
The Way of the Househusband

So apparently this is marketed in the West as an anime, but in Japan as a “motion-comic”. It’s definitely the latter. Absolutely stellar voices, great source material, but it’ll definitely not fit everyone’s definition of ‘anime’ as it’s more sliding stills than anything else.

Read the manga. Or watch the live-action series maybe, I haven’t had time to check it out myself yet to know if it’s better.

Godzilla Singular Point

A Godzilla TV anime? Which actually seems decent?

I love it. Give me more!

Information overload warning. They talk FAST, and there’s plenty of scientific terminology. Great character expressions so far.

Full Dive: The Ultimate Next-Gen Full Dive RPG Is Even Shittier than Real Life!

Another lengthy light-novel title, but.. wait. This show seems.. okay??

It’s definitely your typical VRMMO story as a foundation, but.. they’re not trapped in it? And there’s blood? This is not your run-of-the-mill progression, as far as how the first episode ends up.

also overly egregious fan service, be warned.

It’s Too Sick to Call this Love

It’s not often that I’m feeling like I want to just end an episode early and skip the rest of it during these marathons, but this one takes it. The title is VERY on point.

*sighs* In short, 20-something self-proclaimed kuzu (scum) starts hitting on a high-school girl (a friend of his little sister) who VERY CLEARLY AND VOCALLY DOESN’T WANT ANYTHING TO DO WITH HIM but he doesn’t stop trying to get close to her while the show and everyone around the two of them tries to sell it as “oh it’s cute and endearing” and we’re just here going “NO. STOP THIS SHIT. FFS.”

This isn’t cute. It’s creepy and disgusting. Avoid.

Burning Kabaddi


We were pretty excited to see how this turns out, but at the end of it even our resident sports-anime-superfan went “Pass” for this one. The sport itself just didn’t grab us. Nothing wrong with the production of the show overall though.

Combatants Will Be Dispatched!

The manga is written by the creator of Konosuba, and while this is also comedic in tone it’s nothing like it.

Kisaragi evil megacorp has pretty much taken over all of Earth, so they need more territory to occupy. They specifically select Combat Agent Six (through a diceroll) to be sent on a vital mission to another planet (by means of an untested and highly dangerous teleportation device) in order to do recon for an eventual invasion. They send the AI Alice to help him out with his evil deeds; there’s just one problem. There’s already a Demon Lord’s Army there, and they can’t have two evil orgs there, so they have to do evil stuff to fight evil… or something?

Might watch more, just to see if it ends up going somewhere.

Egrigious fan service here as well.

To Your Eternity

Oh wow. I don’t really want to detail it a lot, but it’s good. It’s brutal and somber and fantastical. It’s the highest rated new show this season (8.71 at the time of writing, with 2 episodes out), and if you’re only watching one show this season this is probably your go-to.

I Shaved. Then I Brought a High School Girl Home.

it’s the ‘Sick Love’ show but actually good and a seemingly healthier relationship

While walking home from getting drunk after being rejected, our 26-year-old main-char-kun finds a highschool girl alone with nowhere to go under a streetlight. He invites her to stay at his place, and when the girl later offers herself up as a reward he refuses to let her, instead mumbling something about “I want miso soup” and falls asleep.

Romcom with potential, depending on where they take it.

Those Snow White Notes

Shamisen playing and Drama. Looking at the poster, we only see one of the characters in the first episode, so I’m excited to see where it goes.

Not a High recommendation, but if you like music and drama you can probably not go wrong here.



Male’s rythmic gymnastics group competition. Middleschool baseball-player-protag-kun stumbles on a rythmic gymnastics group competition on his way home from his last match before high-school, and is captivated by a certain high school’s performance.

If you like sports anime it might be good, but personally there’s too much else to keep up with so a pass for me.

Shadows House

VERY interesting and mysterious. Extremely cute-leaning first episode, but it’s very apparent that it’s just hiding something more sinister.

A house of completely pitch-black ‘Shadows’ employ ‘dolls’ that function as personal caretakers and their ‘faces’/doubles somehow..? Not a lot is revealed in the first episode, instead we’re just with one of these Shadow+Doll pairs and their daily routine.

Interesting. Will continue.

Pretty Boy Detective Club

Produced by Shaft, something Pretty Boys dealing with cases where hearts or something or…

I’ll be honest, I dozed off during this one (it was 4:30 AM, to be fair) so I don’t recall much.

It’s gorgeous (it’s Shaft after all) so I’m probably going to give it a shot just for that, but story wise..? Didn’t really catch me.

(At this point we were only 3 people left, and we only have 3 shows left!)

Don’t Toy with Me, Miss Nagatoro

The last of the ‘girl teases boy’ trifecta to get an anime adaptation (the other two being ‘Teasing Master Takagi-san’ and ‘Uzaki-chan Wants to Hang Out!’) and from what I hear there are a lot of people that like this one over the other two.

And I could see hints of why, as between the teasing this actually seems to show some sort of honest affection instead of the complete airheadedness and spite that people hated in ‘Uzaki’.

If you have an opinion on the other two you probably know what you’ll feel about this one, but if you’re dismissing it simply beacuse of ‘Uzaki’ I’d say give this a shot. (personally, I’m undecided on whether to watch or not)

The Saint’s Magic Power is Omnipotent

Not one but two women get summoned to another world. Upon arrival, one is declared the Holy Saint and gets swept away by the ruling Prince. Meanwhile, our main char, the other woman, is just.. left there? Eventually she finds herself in a research institute, where she begins to learn about this world, including its magic.

I’m not sure we’re getting the full grasp of where it’s going in the first episode, but I really liked it. There’s some drama and an evil-for-evil’s-sake character (the Prince) that I’m not looking forward to seeing more of, but it’s a mostly chill story and decent production values. We’ll see where it ends up.

The Romcom Where The Childhood Friend Won’t Lose!

And we’re ending it on a very… middle-of-the-road note! It’s a school harem romcom, like so many others of its kind, but where the childhood best friend has already been rejected by main-kun and knows that he has unrequited feelings for another classmate! She isn’t giving up just yet though!

Very meh. Not bad in any way, but far from great. Been too many others like it in the past.

Summarising the summaries, here are our recommended series:

  • To Your Eternity
  • Odd Taxi
  • Super Cub
  • Vivy: Fluorite Eye’s Song
  • 86
  • Shadows House
  • Those Snow White Notes
  • I’ve Been Killing Slimes for 300 Years and Maxed Out My Level
  • Shaman King
  • Let’s Make a Mug Too

And my own personal additions:

  • Godzilla Singular Point
  • Mars Red
  • The Ultimate Next-Gen Full Dive RPG Is Even Shittier than Real Life!
  • The Saint’s Magic Power is Omnipotent
  • Good-bye, Cramer

And shows to keep an eye on:

  • Pretty Boy Detective Club
  • Jouran: The Princess of Snow and Blood
  • Combatants Will Be Dispatched!
  • The World Ends With You
  • Tokyo Revengers
  • Dragon Goes House-Hunting
  • Battle Athletess Daiundoukai ReSTART!

And, uh, that’s it? Shout-out to Elof and Bawb who also stuck around to the end of the marathon, and to everyone else who joined in during it.

This just took like… 4 hours to compile. Cool.
Let me know if you liked it, either here in the comments or reach out on Twitter

I’m probably going to go back to sleep for a bit..

me before and after writing this (source: Hyouka)