Kuzu no Honkai follows Hanabi Yasuraoka and Mugi Awaya, who look like the perfect couple to everyone around them. In truth, they are joined by the same private pain: each is in love with someone they cannot be with. Hanabi has loved her childhood friend and neighbor Narumi Kanai for as long as she can remember, and she is elated when he becomes her new homeroom teacher. That hope falters when Narumi is noticed by the music teacher, Akane Minagawa, and a relationship begins to blossom between them.
Mugi carries a similar wound. Akane tutored him in middle school, and he has loved her ever since. After a chance meeting in the hallway brings him and Hanabi together, the two lonely students begin to spend more time with one another. They eventually decide to use each other as substitutes for the people they truly love, sharing physical intimacy in an arrangement built to stave off their loneliness. Beneath the image of an ideal couple, both remain trapped by feelings they cannot resolve.
