The series is set in the same world as Ranma ½
Shirogane proudly declared that Gender Swap Awakened can't be reversed by anything, even hot water. Clearly he had a run-in with Ranma, and the encounter was so weird he remembered that.Shirogane is a closeted Otaku
When he cast Gender Swap Awakened he did quip it couldn't be reversed even by hot water... He has obviously read Ranma ½.