Akiroro's Questions (2)

This is a BL historical manhwa, the MC Getting into the story? Basically, the MC is a teacher and he has two students, a girl and a boy, then he takes in an abandoned child as his student, a boy, a little one, and he knows that his new student will become the future demon king, that's why He tries to stop him, and the lil boy grow fond of him, and the MC who has transmigrated has a lot of knowledge about potions and medicines.Btw, there's also an additional scene where the teacher is kidnapped, and the female student studies with another teacher... Smth like that.

I read this a long time ago, i guess it has ended already.
It's a bnw manhwa (black and white) aka colorless. And it has 2 seme. Like.. similar to "you're my world" One seme is rich and the other is similar to the seme in banana fish.
I don't remember the main male lead but one spesific scene.. the rich seme let uke go with the other seme to run away from something and.. the uke sad..?
If i am right, this one is involved with.. gangster? The seme? Idk.
Tell me the title if you find it, Thank You. ╥﹏╥