THE SMART TRICK OF OSHI NO KO MANGA THAT NO ONE IS DISCUSSING

Unbeknownst to him, Aqua's fraternal twin sister, Ruby Hoshino, will be the reincarnation of Sarina Tendōji, certainly one of Gorou's patients who was a fan of Ai. 4 yrs later on, Ai is murdered in front of the twins by the identical enthusiast who killed Gorou. The fan later commits suicide, but Aqua deduces which the murderer could possibly have