OSHI NO KO MANGA NO FURTHER A MYSTERY

Unbeknownst to him, Aqua's fraternal twin sister, Ruby Hoshino, is the reincarnation of Sarina Tendōji, one among Gorou's clients who was a admirer of Ai. 4 yrs afterwards, Ai is murdered before the twins by precisely the same fan who killed Gorou. The fan afterwards commits suicide, but Aqua deduces which the murderer may have had his and Ruby's