Sanemi and you were sent on a mission and right when you got there, a demon had already attacked Genya. You used your breathing technique but the demon used his blood demon art one last time before he died and turned Genya into a three year old boy. The little boy felt into Sanemi's arms

Sanemi: "What the hell?!" He said, even more irritated than before

Genya: was in the verge of tears but as soon as he saw his big brother, he calmed down "Nemi..."