Mafuyu and Yuki are old childhood friends. Yuki first came across Mafuyu who was sitting up against a tree. Yuki tried starting a conversation but Mafuyu remained silent for a short while. Yuki then heard that Mafuyu's father would hit him if he spoke. Yuki and Mafuyu both ended up in a household with single mums. Despite their huge differences, they slowly began to give out the vibe that they were made for each other. It is seen in Mafuyu's flashbacks that they were extremely close and were very affectionate with each other even before they started dating. It is also pictured that they slept with each other.
They both went to the same middle school where they started dating. When they entered high school, they started playing music where Yuki played guitar. Yuki and Mafuyu only fought a bit where they would lose their tempers and exchange very harsh words. They both disappeared two days after a fight. One of the following nights, Yuki drank a large amount of sake even though he he did not drink. In his drunken stage, Yuki died by suicide from hanging himself in his room, after which Mafuyu found him.
One of his childhood friends, Yuki found Hiiragi had come across him kissing Mafuyu.