Jin; The angelic kingka in school. He's so pure and inncocent with an addition of being good looking, making all the girls swoon over him. 

Yeonseo; The rough & rude kind of girl probably left with only 20% of her feminity. It became a habit to say vulgarities.

Who wouldnt be shocked when the two opposites became an item? Indeed, they became a hot item in school but in a bad way. Their schoolmates kept giving the disgusted looks and assumed some stuffs. Yeonseo especially felt angry about this but Jin tried his best to comfort his now official girlfriend.