Expecting to be living alone and free for three months as his parents go on a business trip, high schooler Shuuto Sakaguchi is surprised to come home to a young girl he's never met before. It turns out she is Chiho Norita, the daughter of one of his parents' colleagues, and he has to take care of her for the next three months. Shuuto, who knows nothing about childcare, develops a strong bond with Chiho over the next hundred days.
Hyakunichikan!! (literally "100 Days") is an Iyashikei manga by Kokone Nata, published from 2015 to 2017 in Tonari no Young Jump.
Provides examples of:
- Accidental Misnaming: Hisaki's sister constantly calls Shuuto and Chiho by the wrong names. "Shota" or "Shuntaro" for Shuuto, and she's called Chiho "Chiyo", "Ochinchin", and "Cheetos". Lampshaded by Hisaki.
- Anger Born of Worry: Shuuto very lightly slaps Chiho when she wanders off looking for Fukumen and gets lost in the neighborhood. He stands impassively as she cries, telling her how much he worries about her.
- Animal Lover: Chiho with Fukumen the rabbit, and Hisaki's mom runs a veterinary clinic out of her house. His sister is training to be a pet groomer.
- Animal Motifs: Chiho is often compared to a rabbit, especially in Chapter 11, when she brings home a stray one.
- Aw, Look! They Really Do Love Each Other: Hisaki and his big sister tease each other a lot, but Shuuto explains to Chiho that they fight because they're close. Chiho asks if she and Shuuto should fight to become closer.
- Beauty Is Bad: Discussed separately by Shuuto and the kindergarten girls, regarding Masaki-sensei. However, he turns out to be a Sheep in Sheep's Clothing.
- Bishie Sparkle: Kanami's Crush Filter makes her see Shuuto with these. Masaki also gets some when he's introducing himself.
- Blush Sticker: Chiho tends to get these.
- Cannot Keep a Secret: Komugi easily forgets she's not supposed to share all the details of her big sister's crush, or that she padded her swimsuit.
- Child Care and Babysitting Stories: The manga begins when Shuuto unexpectedly is tasked with taking care of grade schooler Chiho, the daughter of his parents' friend, for 100 days. Shuuto grows close to Chiho over the 100 days in spite of his lack of knowledge of child-rearing.
- Cheerful Child: Chiho and her friend Komugi are the most consistently cheerful. Kanami is usually being a Tsundere, and Sakura tends to be overly serious.
- Cicadian Rhythm: Chapter 34 opens with cicadas to show it's summer break.
- Corner of Woe:
- Shuuto doesn't go into a corner, but he does tend to grow mushrooms when he has his head down on his desk in despair. In contrast, Aoki grows a flower from his head to emphasize his positive attitude.
- Tanaka goes into a corner of woe when Kanami calls him an "old man" (he looks to be in his 20s).
- Delinquent Hair: Small children like Chiho tend to think Hisaki Aoki is a delinquent because of his blond hair. He's actually a Nice Guy.
- Embarrassing Damp Sheets: In Chapter 9, Chiho wets the bed and is embarrassed about it. When Shuuto sets the futon out to dry, his neighbors think he did it, since they don't know about Chiho.
- Expressive Hair: Chiho's pigtails flip up like rabbit ears sometimes to show her emotions.
- Festival Episode: Chapters 31 and 32 have Shuuto, Aoki, Chiho, Kanami, and Tanaka going to a summer festival. The girls wear child-sized yukata. In Chapter 46, they all go to a fireworks festival with Masaki, Ishima, Komugi, and Hatayama, and everyone (except Tanaka) wears a yukata.
- Friend to All Children: Masaki. Understandable since he's training to be a kindergarten teacher. Also Aoki and Shuuto, though they understandably focus mainly on Chiho.
- From the Mouths of Babes: Chiho's kindergarten classmate Sakura says some surprisingly mature things that make her teacher wonder how old she really is.Sakura: Takumi. If you're always talking down on other people, and you always worry about others, you'll end up in a bad state yourself. And you'll forever be trapped in desolation.
- Girlish Pigtails: Chiho normally wears her hair in two pigtails, similar to Chiyo from Azumanga Daioh.
- Got Volunteered: Shuuto wasn't consulted at all before he was assigned to take care of Chiho.
- House Husband: Kouji remarks that Shuuto has "the skills of a housewife".
- Kabedon: Discussed in the omake for Chapter 11.5, where Chiho asks Shuuto and Aoki what it is. They pretend not to know, to preserve her innocence. In Chapter 20, Komugi says her big sister reads a lot of shoujo manga and wants it to happen to her.
- Kindly Vet: Mrs. Aoki, Hisaki's mom, is a vet who checks the rabbit's health. Hisaki appears more often, though he's not technically a vet.
- Last-Name Basis: Aoki calls Shuuto by his first name, but Shuuto calls him by his surname. In Chapter 34, Chiho thinks this means they aren't really friends, triggering a Heroic BSoD from Aoki.
- Meaningful Name: Shuuto names the rabbit Fukumen, meaning "mask", since its markings make it look like it's wearing one.
- Minor Living Alone: Shuuto is a high schooler living on his own (except for Chiho) for three months while his parents are overseas.
- Mistaken for Romance:
- Chiho's friend Kanami thinks that Shuuto must be married to Chiho's mom, but also assumes he's hitting on their kindergarten teacher (just because he was talking to her).
- Later on she thinks that because Shuuto and Ishima went to go buy snacks for everyone together that means they're dating. And then when Ishima dismisses him they suddenly broke up. She has a very 5-year-old understanding of relationships.
- Shuuto's friend Hisaki Aoki assumes the reason he's been so secretive and distant lately is that he got a girlfriend.
- Necktie Leash:
- Chiho and her friends pull Shuuto around by his school uniform's tie when Playing House, where he's the "dog".
- Kanami grabs her servant Tanaka by his tie when she's trying to make Shuuto jealous.
- Not What It Looks Like: Kouji tells his sister this when she sees him holding a pair of Chiho's underwear on Shuuto's balcony (he was hanging up the laundry for them). It doesn't help that she already suspects him of being a paedophile because he likes Magical Girl shows.
- Ojou: Kanami is a kindergarten version, though the only one who really treats her like a princess is her caretaker Tanaka.
- Ojou Ringlets: Kanami has one on the side of her head, indicating her upper-class background. In the aquarium chapter, she has two.
- One of the Kids: Aoki tends to behave more childishly than Shuuto, especially when he's around Chiho or other kids her age.
- Parental Substitute: Shuuto becomes this for Chiho.
- Pool Episode: Chapters 38-39, though they start shopping for swimsuits in Chapter 36.
- Pretty Boy: Hara Masaki is noted to be handsome In-Universe, even by his kindergarten students. The other teachers think he must be from an idol agency.
- Scooby Stack: Sakura, Komugi, Chiho, and Takumi all do this in Chapter 16 to spy on Kanami.
- Shout-Out:
- Sometimes Chiho has an Imagine Spot of herself in a Super Sentai type costume, with a helmet shaped to fit her twintails.
- In Chapter 18, the movies Shuuto suggests he and Chiho watch are My Neighbor Totoro, Spirited Away, and Kiki's Delivery Service.
- The cover of the third tankobon, with Chiho holding sunflowers, evokes another manga about a little girl and her father figure.
- A few moments when Chiho's pigtails fall off in shock are similar to a scene from Azumanga Daioh where Osaka fantasizes about detaching Chiyo's pigtails.
- Show Within a Show: Kouji is a fan of the Magical Girl show Asafuru (Cheer Princess), and introduces it to Chiho.
- Sick Episode: In Chapter 23, Shuuto has a fever and Aoki and Kanami come over to help Chiho take care of him. They end up making rice porridge with...creative...ingredients.
- Sink or Swim Fatherhood: The premise of the manga.
- Sleep Cute: A non-romantic version: In Chapter 34, Chiho and Shuuto are cuddling when Aoki comes by. In Chapter 42 Shuuto wakes up to see Chiho and Aoki after he spent the night.
- Sneeze Cut:
- In Chapter 10, Shuuto sneezes and Aoki mentions Chiho must be talking about him (she was).
- In Chapter 13, the same thing happens to Kouji when Shuuto mentions him.
- Suspiciously Specific Denial: At the pet store, Shuuto's kohai Mika Mimori hides her face and says she's "definitely not a first-year Class B student from Amanatsu High!!" He doesn't remember who she is even when she uncovers her face and mentions her name.
- Teru-Teru Bōzu: In Chapter 10, Chiho's kindergarten class makes these, and later she and Komugi dress as teru-teru bozu. Aoki also gives Shuuto one. The title page for the chapter has one hanging from Shuuto's leaf umbrella.
- Tiny Tyrannical Girl: Kanami is rather bossy for a kindergartner, though it's not surprising for a girl whose parents hired a private caretaker for her.
- Tsundere: Chiho's friend Kanami is one with a Precocious Crush on Shuuto, getting jealous when the other girls play with him.
- A Wild Rapper Appears!: When Chiho is lost at the aquarium, a man and woman come up to her, and the man starts rapping for some reason. She thinks he's a Kappa (pronounced similar to "rapper" in Japanese).
