She's around 15-18. And HE has a grown daughter and was in retirement. Even if she's "of age", she's still a child...and is referred to as just that: a child. HE called her a child. Do we see why this is wrong?
Yeah i'm sure her appearance has nothing to do with it either...she's 17 yet looks 12 and every chapter we have a random feet pic. Still getting sexualized and still is a minor.
Some historical good educational historical manga (with a bit of fiction included in plot):
Fushigi no Kuni no Bird
The Apothecary Diaries
Sengoku Komachi Kuroutan: Noukou Giga
A Sign of Affection has a couple that realizes their mutual feelings quickly, but the female mc does take a decent amount of time to adjust to physical affection.