Four childhood friends enter an unusual living arrangement when they inherit a house and four million yen from an elderly woman they called Haru. Yuka Ota is innocent and gentle, Kasumi Niiyama is sexually curious and forward, Kosei Horie tends to be evasive, and Ryuhei Onosaka is easily smitten and romantic. Given the opportunity to live alone together in a rural house for one year, these two boys and two girls who have grown up almost like family suddenly find themselves sharing a roof during their high school years.

As they settle into their new life, the close quarters force each of them to reconsider what they truly mean to one another. The central question becomes whether they are simply friends, something like family, or potential lovers. Kasumi, driven by her sexual curiosity, begins testing the boundaries of their relationships, while Yuka remains hesitant and unsure. Kosei attempts to maintain distance and avoid the complications developing around him, even as Ryuhei's romantic feelings grow increasingly obvious. The story follows their awkward and slightly erotic coming of age as they navigate love, friendship, and physical desire under the same roof. Each character must decide what rules apply to their shared life and whether crossing the line from childhood friends to something more intimate is truly possible.