demonic.black.cat's Favorite

It's a manga about a female teacher and male student. I can't remember exactly but i think the student made a bet on getting the teacher to fall for him but she turns out to be real tough to get. There was a scene where they were all in class and the student asked her "If both you and your bestfriend were to like the same guy, what would you do?" and she answered "I'd snatch him away before my bestfriend has a chance" Please help me find this it's been bothering me for days...Thanks :')