Second-year student Tachibana Kaoru is completely heartbroken by her middle school homeroom teacher, Shimotsuki Mirei. Fellow classmate Minagi Shiori witnesses it and listens to Kaoru's story. Then Shiori poses a question: instead of forgetting someone you cared about, is it possible to simply overwrite those memories with different ones? She makes a request — help me go through my past memories to forget my older brother. The two begin a tour of Shiori's past, each wanting to move on from someone. When their classmate Inohara Riku — who has feelings for Shiori — discovers what they are doing, the curtain rises on a bittersweet, sometimes slapstick, poignant love story.