Sink or Swim

Synopsis

Oka, Mao, Kadoi and Hasumoto are good friends who study in a technical school. One day, Kadoi confessed that he and Hasumoto have been dating in secret. Then, Oka and Mao overheard moans from the room next door. Since then, Mao, who have been interested in sex between men, approaches Oka. However, Oka has started being more conscious of Mao for another reason... (Source: Kadokawa, translated) Included one-shot: Hajimari no Period