|Family|| Aizawa (father)|
Kai Nanami (father)
Kai Nagase (half-brother)
Kano Kozuki (half-brother)
|Relationships||Kai Nagase and Gaku Ichikawa (lovers)|
Ren was "born" after Kai Nanami was raped by Aizawa. Aizawa stole and fused their DNA, creating Ren. However, neither Aizawa or his half-brother, Nagase, liked Ren and both disdain and even go as far as to hating him. It is implied in Mou Matte and Sweet Trap, the games' spin offs, that Ren was given to foster care and became orphan.
Ren admits in Mou Matte and White Flower that he has a crush on Nagase, but is also in love with Gaku. While Nagase disdains Shiina, he accepts this, and the three start a three-way relationship.