The series is structured to show Ryuuki's gradual "graduation" into maturity:
: Introduces Ryuuki’s isolated life and his sudden infatuation with the mysterious Kiriru, culminating in their first unexpected meeting. shounen ga otona ni natta natsu cap 1 2 3 sub top
: Ryuuki’s "Cool Big Sis" who is a brilliant scientist but unkempt in her daily life. She adopts the Kiriru identity to connect with her brother in a way she feels her true self cannot. The series is structured to show Ryuuki's gradual