Summary: Oota Katsuyo is a 15-year-old girl just entering high school. She’s short and plump, thanks to being the daughter of a family that runs a tonkatsu shop. She’s followed her crush from middle school to the same high school, and she’s devastated when she finds out he’s not interested in chubby girls. As she’s looking for ways to lose weight, the free-spirited president of the swimming club, Itou Hatsume, and her serious and demanding vice-president, Kaji Rinko, are looking for new members to supplement their roster of two. When Katsuyo meets Kaitani Ayumi, a rail-thin girl with an appetite that matches her own, Ayumi drags her to the swimming club to join up. Will Katsuyo have problems measuring up to the demands of the swimming club, or can she make a big splash?
A cheerful 15-year old girl just entering high school, Katsuyo loves eating tonkatsu, but she’s suddenly looking for ways to lose weight after she overhears her crush rule out chubby girls from romantic consideration.
A tall and skinny girl in the same class with Katsuyo. She’s noisy, talkative, and loves eating. She’s Katsuyo’s first new friend in high school. Calls herself Ayu-tan.
The swimming club president. A bit of an airhead and a free-spirit, but also very happy and friendly. She keeps the swimming club having fun. Nicknamed Hattsuu.
The swimming club vice-president. She’s the stern and strict member of the group that tries to keep everyone on track. She hides a surprisingly cute side at the same time. Nicknamed Kajirin.
Katsuyo’s childhood friend. A reserved, sarcastic guy, but a good friend to Katsuyo. He seems to be hiding something, though.
Katsuyo’s middle school crush. He’s a grade above her, and Katsuyo followed him to their current school.
A duck that lives in the school’s outdoor swimming pool. An honorary member of the swimming club.