I Definitely Don't Have a Crush on Mr. Saeki

I, Yuka Takanashi (16), am in love with my math teacher, Mr. Saeki...! He's sweet, smart, handsome... I want to get to know Mr. Saeki better. It turns out Mr. Saeki is engaged...! If I'm going to give up on him, I need to at least tell him how I feel... "Mr. Saeki... I... like you..." "Hm. Fine. I'll go out with you... if you're okay with being second." "I don't really like girls like you." Mr. Saeki... is actually more of the rough type?! There's no way I can love a guy like that...! That's what I thought at least... but why can't I keep myself from going back to him... bittersweet... a true forbidden love comedy about a teacher and his student!

(Source: MangaPlaza)