THE ULTIMATE GUIDE TO OSHI NO KO MANGA

Unbeknownst to him, Aqua's fraternal twin sister, Ruby Hoshino, may be the reincarnation of Sarina Have a tendencyōji, among Gorou's individuals who was a enthusiast of Ai. Four several years later, Ai is murdered in front of the twins by precisely the same enthusiast who killed Gorou. The admirer later commits suicide, but Aqua deduces the murder