He was a medical doctor specializing in obstetrics and gynecology and the one responsible for delivering Ai Hoshino's baby. He was later killed by a stalker of Ai and, ironically, got reincarnated as her child, Aqua.

Audition lines:

1) This story is a work of fiction. Actually most everything in this world is fiction. They fabricate...exaggerate...and thoroughly conceal anything inconvenient. That being the case, the idol is one who wants to be skillfully lied to. In this world lies are weapons. 

2) You're fine the way you are, Sarina. There's no need for you to be reborn.