
Seiri-chan is a heartwarmingly absurd manga for the modern period.
Like a lot of manga, Ken Koyama’s Seiri-chan is named after its protagonist. However, even longtime fans of anime/manga may be struggling to remember another franchise with a character named Seiri in it.
That’s because Seiri isn’t a traditional Japanese name. Instead, it’s the word for “period” or “menstrual cycle.”
Yes, Seiri-chan is the latest, and arguably most unexpected, entry in Japan’s ever-lengthening list of anthropomorphized characters, following colleagues drawing inspiration from mushrooms and Japanese swords. Rather than trying to render the liquid state of monthly lady flow, Koyama draws Seiri-chan as a pink, vaguely heart-shaped entity with full red lips and a white cross for a nose.
While Seiri-chan can be seen punching a woman in the midsection on the back cover of the first collected volume, she’s generally presented as a more benign figure in the manga. Each chapter has Seiri-chan spending time with different women during her once-a-month visit, often as they’re experiencing some sort of personal crisis or emotional dilemma. For example, in the scene below, Seiri-chan makes her long-awaited appearance in front of a woman named Kaori, who recently slept with a married coworker with no contraceptives being used. “Men who don’t use a condom are the worst,” Seiri-chan declares, while giving Kaori a reassuring hug.
▼ “I don’t know what I would have done if you hadn’t shown up today,” says Kaori, relieved that the night of passion hasn’t resulted in an unwanted pregnancy.
In a later chapter, Seiri-chan gives a pep talk to convenience store clerk Riho, who’s always had an inferiority complex about her less-than-glamorous looks and thus is unwilling to believe the handsome man who confessed his love to her is serious about wanting a relationship.
Seiri-chan also takes time to console Momoko, a cafe waitress and aspiring novelist who’s been sent into a spiral of depression after discovering that her coworker Ippei, who she had a secret crush on, has started dating the beautiful half-Japanese Chloe, yet another of her coworkers.
Sometimes, though, instead of being quietly supportive, Seiri-chan is psychotically violent, like when she punches this man in the face while shouting “Menstrual Punch!” before injecting him with a drug that causes him to have periods as well.
Through written and illustrated by a man, Seiri-chan has quickly built up a sizable female fanbase, including our own female Japanese-language reporter Anji. “Koyama’s a guy, so how does he understand women’s feelings so well?” said Anji after reading through the volume. “Whether I’m laughing or crying, I can always identify with the women Seiri-chan visits.”
With its outlandish premise and episodic nature, Seiri-chan seems like it’d be a perfect fit in the world of late-night short anime programming, and we wouldn’t be surprised to see an adaptation in the near future. Who knows, maybe the franchise will become a big enough hit that we’ll see a brand-new batch of anime-themed menstrual pads go on sale in Japan.
Photos ©SoraNews24
[ Read in Japanese ]






Massive menstrual flow character will be Japan’s newest movie star
We get our first peep at Seiri-chan, the Japanese movie all about a menstrual flow mascot
Japan’s newest cute mascot character’s mission is to go up your butthole
IT infrastructure becomes cute anime girls in Japan’s latest educational anthropomorphism project
Japan’s craziest train station has a giant with light-up eyes growing out of its wall【Photos】
Tokyo government organizes food truck event to clear out delinquent/homeless teen gathering area
Japanese onsen egg maker from 100-yen store Daiso needs to be on your shopping list
We go looking for a monkey mommy like Punch with Amazon Japan’s ultra low-rated orangutang plushy
Virtual idol Hatsune Miku redesigned with look that adds new elements and brings back old ones
Universal Studios’ Sailor Moon theme park attraction is finally coming to America
Starbucks Japan releases new My Fruit³ Frappuccino at only 34 stores around the country
This Japanese vending machine doesn’t sell drinks, but you can buy drinks through it
The top 10 graduation songs in Japan as chosen by current Japanese high school students
Studio Ghibli’s “Bouncing Totoro” zoetrope gets its own merchandise at museum
Tokyo’s teamLab most visited museum in the world, officially more popular than Van Gogh
Train station platform ramen store closes its doors on half a century of history in Tokyo
Studio Ghibli releases Catbus pullback keychain that runs like the anime character
Studio Ghibli adds new Mother’s Day gift sets to its anime collection in Japan
The next time you’re feeling stressed out, you could relax on a Pokémon Psyduck chair from Japan
Cherry blossoms begin blooming in Japan with record-early starts for sakura season
Komachi Shokudo: Japanese mum’s-style cooking for breakfast, lunch and dinner in Tokyo
Starbucks Japan unveils new sakura cherry blossom collection for hanami season 2026
The 10 most annoying things foreign tourists do on Japanese trains, according to locals
Nine great places to see spring flowers in Japan, as chosen by travelers (with almost no sakura)
Starbucks Japan releases new sakura goods and drinkware for cherry blossom season 2026
Starbucks Japan releases first-ever Hinamatsuri Girls’ Day Frappuccino
Japan’s cherry blossom season predicted to start earlier than we’d thought, especially in Tokyo
Survey asks foreign tourists what bothered them in Japan, more than half gave same answer
Japan’s human washing machines will go on sale to general public, demos to be held in Tokyo
Starbucks Japan releases new drinkware and goods for Valentine’s Day
We deeply regret going into this tunnel on our walk in the mountains of Japan
Studio Ghibli releases Kodama forest spirits from Princess Mononoke to light up your home
Japan’s newest Shinkansen has no seats…or passengers [Video]
Major Japanese hotel chain says reservations via overseas booking sites may not be valid
Put sesame oil in your coffee? Japanese maker says it’s the best way to start your day【Taste test】
No more using real katana for tourism activities, Japan’s National Police Agency says
Testing Japan’s sold-online love potion: Mr. Sato makes his coworkers drink the romantic mixture
Here’s what happened when our biggest male otaku tried out Japan’s new Manga Genic eyeliner【Pics】
We try to destroy Japan’s sturdiest eyeglasses with the power of Mr. Sato’s butt【Video】
Meg tries out Starbucks Japan’s newest treat: the White Brew Coffee and Macadamia Frappuccino
We go looking for a monkey mommy like Punch with Amazon Japan’s ultra low-rated orangutang plushy
New book compiles taste tests of shampoos used by 30 of Japan’s top anime voice actresses
This is Japan’s second-shortest mountain, and we climbed it without realizing it【Photos】
Testing Japan’s stick-on, mask-your-pooping-sound speakers against our coworker’s butt【Video】
A singalong song from Japan to surpass “Paprika?” Presenting “Karaoke Neko-chan”【Video】
Tokyo’s Cardcaptor Sakura exhibition has giant Kero-chan, free cosplay, and English signage
Haru Urara, Japan’s winless “Star of the Losers” race horse, has passed away
The time farting lead to murder and the fall of one of Japan’s great samurai clans
Our male otaku tries Japan’s anime heroine mascara, learns what it’s like to be shojo manga star
What would the cast of Japan’s longest-running anime look like in real life? Kind of terrifying
SoraNews24’s Otaku Aniki is here to give you the three must-watch anime of the spring season【Vid】