Naoto Watari has had his share of struggles: his parents died two years ago, and now he and his sister live at his aunt’s house. There, his desire to protect his sister earned him notoriety as “the guy with the sister complex”—which never mattered to him, as his sister always came first. But when Satsuki, a childhood friend-turned-enemy(?), becomes his school mate, Naoto’s ordinary life is thrown into chaos … and Satsuki may just be the beginning.
Realizing that he's been unconsciously hurting Satsuki, Naoto heads to her apartment to apologize to her. However, he learns that she is dating his friend Tokui, and has gone back to her home in Matsumoto. This seemingly unbelievable turn of events leaves Naoto shattered. Three months then goes by, and his desire to see Satsuki only grows stronger with each passing day. One day, he decides to call the inn her adoptive parents run in order to ask about the photo she wants, only to learn yet another shocking truth!! Naoto later goes on a field trip to Okinawa with his classmates, one of whom is his ex-girlfriend, Ishihara-san. However, thanks to some words of advice from Tokui, the two of them manage to grow closer during the trip!