An unhappy girl who engages in self-harm, a high schooler ostracized by her classmates, and an old woman looking to live out her twilight years in peace - what could three such different people have in common? That's what grade schooler Nanoka Koyanagi is trying to find out. Assigned by her teacher to define what "happiness" means to her, Nanoka tries to find her place in the world by exploring her relationships with these three strangers, and through them, comes to know herself.