High School Ninja Girl, Otonashi-san (also known as Kunoichi Joshikousei Otonashi-san) is a Slice of Life Yonkoma manga by Masami Watabe that is about Exactly What It Says on the Tin. Fuka Otonashi has just transferred to a new school, and she is also a ninja.
The various chapters show us how a ninja like Otonashi handles day-to-day life. Like any girl, she deals with her crush on otherwise ordinary boy Arima, suffers Weight Woes when she puts on extra pounds over the holidays, works a part-time job, confronts her Childhood Friend-slash-rival ninja, takes on an American fan of ninjas as her apprentice, and much more.
Other characters include Makoto Arima, the boy Otonashi-san has a crush on; Otonashi's older brother and resident Butt-Monkey Yoichi; Kei Shimura, a childhood friend and ninja rival of Otonashi's who crossdresses because the only thing he can beat Otonashi at is femininity, and Hitomi, Otonashi's best friend (thanks to the great lunches she can make).
The manga ran from 2013 to 2015, for a total of 65 chapters. The manga is officially available in English via MangaBox.
High School Ninja Girl, Otonashi-san contains examples of the following tropes:
- Abhorrent Admirer:
- Accidental Pervert: While visiting a sick Otonashi-san (and learning she was faking), Arima winds up on top of her and, in the process, her mask begins to slip off. Combined with Our Nudity Is Different, this gets Arima in hot water with Otonashi's mother when she walks in.
- A-Cup Angst: Otonashi-san pads her bra and doesn't take kindly to seeing how much better stacked her friend Hitomi is compared to her during a pool episode (especially since Hitomi is shy about being seen in a bathing suit). Chapter 42 features a class of kunoichi, all separated by bust size. While there is an 'A' class, Otonashi belongs in the "Super A" class. It mostly involves complaining about the H's.
- Bears Are Bad News: During the Horrible Camping Trip in chapters 40 and 41, Otonashi and Arima meet one that matches Otonashi's every move. It ends up being Yoichi in a bear suit, harassing them because he wasn't invited.
- Big Eater: Otonashi-san for several reasons: she snuck in her lunch during class on literally the first page of the manga; she joined the cooking club for the food; she became friends with Hitomi because the former liked the latter's lunch the best; and she filled her entire school bag with rice balls to eat them any time she can. Any time.
- Yoichi Otonashi — He fails to graduate and thus is convinced he needs to attend school with a paper bag over his head to avoid shame. He also somehow suffers the various traps set up inside the Otonashi home despite, well, living there.
- Kei Shimura — He crossdresses because femininity is the only thing he's better at than Otonashi-san. He is constantly the victim of physical abuse from Otonashi, although he tends to deserve it more often than not. He is the undeserving victim of Arima once, though — but this was an accident.
- The Chikan: Played with. Suzuki likes to put discount tag stickers from the supermarket on and under the skirts of girls on the train. He fails against Otonashi-san, starting their rivalry.
- Childhood Marriage Promise: Togawa claims Otonashi is his fiance because of this. He even presents a document — that is stamped with blood.
- Christmas Cake: Literature teacher Aya Kunitachi is still husband hunting at 30. Her personal crush, Kariya, rejects her specifically for this reason.
- Closet Geek: Hitomi is secretly a manga artist. She opts to tell the truth when Otonashi-san suggests she's looking at porn instead.
- Competition Freak: Arima's mother is highly competitive. Growing furious if she thinks someone's going easy, yet getting furious if she loses.
- Crossdresser: Otonashi-san's rival, Kei Shimura takes up crossdressing because feminitiy is the only area where he excels over Otonashi-san.
- The Cuckoolander Was Right: Turns out that Tom was right. Ninjas actually can breathe fire.
- Disproportionate Retribution: Otonashi-san is on a generations' long quest for revenge on Kariya-sensei because one of her ancestors stepped in the droppings of a bull owned by the Kariya's ancestor in front of the girl he liked. Fortunately, Otonashi-san is satisfied with a non-fatal shuriken to the back.
- Distant Finale: Two years have passed when the epilogue hits, but it is still a time skip.
- Elaborate Underground Base: The Otonashis' house is a trap-filled underground lair.
- The Faceless: Otonashi-san's mother, who is only ever seen standing behind another person.
- Hard-Drinking Party Girl: Arima's mother. Her dinner consists of one big bottle of booze. According to Arima, her personality really comes out when she drinks.
- Horrible Camping Trip: Chapters 40 and 41 feature Otonashi, Arima, Shimura, and Hitomi lost in the woods, without a lot of food (because Hitomi brought an electric cooker and Otonashi brought spiked rice balls for a game). Then they meet a bear that out-ninjas Otonashi (actually Yoichi in disguise).
- Identical Stranger: The real reason that Kiraya-sensei doesn't want go out with Kunitachi-sensei is because she looks exactly the same as his older sister. They're personalities are practically identical as well, and they both have a crush on him.
- Jerkass: Suzuki, the supermarket clerk. He complains about being unappealing to women and sticks discount stickers to their skirts because he thinks they deserve it for ignoring him. He doesn't take kindly to Otonashi showing him up so he takes smug joy in 'beating' her at various contests.
- Last-Minute Hookup: As far as the reader is concerned, the final pages of the manga show us Shimura and Hitomi, and Kariya and Kunitachi.
- Lethal Chef: Otonashi-san's aware enough of it, too, that she tricks Shimura into being her taste tester.
- Love Potion: Arima accidentally drinks one made by Shimura. He pursues Otonashi relentlessly until it passes out of his system.
- Non-Uniform Uniform: Otonashi-san wears, along with her sailor fuku, a ninja mask, leg wraps instead of socks, armor under the uniform, and a headband. She manages to convince a teacher doing a uniform inspection that all of these are legitimate.
- Nosebleed: Otonashi-san's response to overhearing Arima saying he wanted to hear her sing.
- Occidental Otaku: Exchange student Tom is this towards ninja.
- Oh, Crap!: Kunitachi quickly develops this reaction whenever Otonashi gets involved in her life.
- Only Sane Man: Arima, by virtue of being the most normal person in the cast.
- Ordinary High-School Student: Arima is just a normal guy.
- Our Nudity Is Different: According to Otonashi-san's mother, taking off a kunoichi's mask is the same as taking off her underwear. This gets Arima into hot water when she walks in on an Accidental Pervert moment during which Otonashi's mask fell off (reveaing a cold mask underneath).
- She Is Not My Girlfriend: This was Arima's response to his mother when she said that Otonashi was no good for her son (since she wasn't rich). However, he said that if he did fall in love with her, it's none of his mothers business.
- Shout-Out: Otonashi's ambition after high school is initially to be king of the pirates. Although it mostly involved sailing around the world on a rubber raft while eating rice balls.
- Sins of Our Fathers: Otonashi-san's quest for revenge on Kariya-sensei is due to an incident between their ancestors.
- Temporary Bulk Change: Otonashi-san puts on a lot of weight over the holidays. She sweats it all away after being forced into close proximity to or having romantic dreams about Arima. It is implied that rapid heartbeats caused by both instances contributed to the even more rapid weight loss.
- Tomboy: Being a ninja aside, it's telling that the only area Otonashi's male rival can beat her in is femininity.
- Trademark Favorite Food: Otonashi-san really likes rice balls.
- Unknown Rival: Suzuki the Supermarket Clerk wants to one-up Otonashi-san, but she consistently outdoes him without even being aware of this.
- Vitriolic Best Friends: While Shimura claims to be Otonashi-san's rival and was initially quite hostile, most of the time he seems happy to hang out with the group and they in turn have few qualms with him. From time to time he'll try tricking Otonashi-san but for the most part he's just another one of the gang.
- The Voiceless: Otonashi-san can communicate instantly through "freakishly expressive gestures." The most we've ever heard is a yelp when she trips and falls. She makes damn sure she's the conductor for the choir event, too.