Marriageable age for female on ancient chinese is 14 y o, n male is 16 y o. Especially on noble famillies, they even betrothed their daugther from young age, even when she was a baby. Meanwhile the boy will interract with their future wife even since she was a super young girl, kinda like dating phase. hence telling the main male lead Pedhopile only because he is fall in lov to a 13 yo girl is kinda wrong i think, as the girl is already at appropriate age to be admired at that time.
