Senpai is a nerdy high schooler whose manga work is discovered by some loud girls in the library. They all tease him, but one among them, Nagatoro, takes it further than the others.
Naoto buys an erotic vampire manga which Nagatoro steals. The next day she proposes a game of accurately poking where each other's nipples are under their clothing, with the prize of a ticket to force the loser to do any one thing without refusing. Naoto agrees, hoping he can force her to stop teasing him.
It's raining when Nagatoro and Naoto are on their way home. After finding shelter, Nagatoro invites him to her home which is close compared to his long walk home. Unable to leave after she puts his wet clothes in the dryer Naoto is invited to play games. Being an experienced gamer, Naoto plans to defeat her as revenge. The next day Naoto is unable to find anywhere to sit at lunch and is forced to sit with Nagatoro and her friends.
Maki and Yoshi tease Naoto about being a virgin and force him to squeeze Maki's breasts. They flee when Nagatoro arrives. Later, while posing for his drawing, Nagatoro notices Naoto is distracted watching a classmate, the champion of the baseball club, and deduces he is jealous of his popularity. She points out he can't expect praise for his talents if he never praises other people either and demands him to praise her.
Nagatoro offers to trim Naoto's long hair and he eventually agrees, but she is called away by Maki and Yoshi who capture Naoto and threaten to shave his entire head. Later, during a heatwave, Nagatoro insists they get shaved ice.
Naoto is surprised Nagatoro doesn't invite him to the summer festival so he goes by himself and bumps into Maki and Yoshi. They send a picture of Naoto on a leash to Nagatoro so she rushes to the festival where Maki challenges her to win Naoto back.
Naoto becomes obsessed with a new game and forgets to study. Nagatoro warns him that if he has to repeat the year that he would end up in the same class as her. Later, Nagatoro overhears Naoto with Maki, Yoshi and Sakura sounding suspicious and bursts in on them. After school, Nagatoro challenges Naoto to Rock, Paper, Scissors to force him to carry her home when he loses.
Nagatoro makes a bet that Senpai has lewd books in the club room, but things don't go quite as she plans. Sakura has a stalker, and she asks Senpai for help getting rid of him.
Nagatoro notices that Naoto is a slow runner and demands he jogs with her. Naoto needs a model for his latest drawing and Nagatoro teasingly insists on modeling for him. Naoto agrees but only if she wears a cat girl outfit.
Naoto is not confident as the President's previous exhibit was a nude painting of herself. Nagatoro is suspicious at Naoto having kept the painting but does offer to model for him. Naoto refuses, claiming he isn't skilled enough to defeat the President.
Naoto produces paintings of Nagatoro's daily life. Gamo suggests sabotaging the President but Naoto insists he will compete fairly. The festival arrives and Nagatoro and the girls wear cat costumes to promote Naoto's paintings.
