High school student Keisuke Mio cannot maintain romantic relationships with girls; none of his ex-girlfriends felt like they were truly together when they were dating him. On a walk home from school, a torrential downpour forces him to seek shelter under the awning of an apartment, where he spots a lone umbrella leaning against the windowsill. As he tries to take it, Mio is promptly scolded by university student Kakeru Yugi—the owner of both the umbrella and the apartment. Mio is taken by surprise when Yugi suddenly orders him to take the umbrella as far away as possible. Despite this odd command, Mio later goes to return the borrowed item, only to be goaded into a game of mahjong by Yugi's friend Tachibana. Soon enough, Mio is visiting Yugi whenever he has the chance, realizing that he is slowly falling in love with him. However, when he secretly catches Yugi and Tachibana together, Mio has to force himself to reconsider his developing feelings.