Responses
Secretary has purple (?) hair right?
If so it's Obedient Heritage
No, it is a black & white manga. Anyways thanks for the help. I will read the one you suggest too.
Ch.3 of Mijuku na Kareshi
https://www.mangago.zone/read-manga/mijuku_na_karesh/an/mijuku-na-karesh-chapter-3.html
Seme is high schooler or something. One day he sees his father having sex with his uke secretary and Seme leave home. Later he come back and do shitty things to uke. Uke is actually falling in love in love with him since young. I think uke has long hair.