Hirugao - Vol. 1 Ch. 5

[MangaDex]

 

[danbellucci]

he still has a dad? yikes! hawkward!

 

[JiYanran]

Oh that's why she's so happy. The old man must be fucking her.

 

[Late_Komei]

Uh-oh

 

[Joe17mama]

Oh that's why she's so happy. The old man must be fucking her.

Lmao ditto, my same thoughts. I thought initially that it was maybe bc she was jealous about him peeping on other girls (besides herself) so telling him off felt good for her, but looking back at her masturbating before and wondering when was the last time... it might point towards your conclusion.