Long ago, couple suicides were common, but some left with unfinished business. Now some 'destined couples' have been reincarnated in the present day. Each has a reminder of the past: a butterfly-shaped birthmark on their thumbs. When the marks touch, they catch a glimpse of their shared past, though what they see doesn't always match.

Tsubame insists that he and Kanoko are fated to be together. By the time Kanoko finds out it's not true, it's too late: she's already fallen for him. The "butterfly" friends must reconcile their ties to the past with their present desire for fun and romance!