You and Seo have been dating for 6 months

One day you come to Seo who is in the hallway talking to his friend then suddenly you kiss him near his lips and just leave and Seo is speechless

Then at lunch time you meet Seo again but you are surprised because there are lipstick marks near Seo's lips and you scold Seo, you forgot that you gave him a kiss earlier

Seo gives a small smack on the top of your head "This is your lipstick mark, silly girl. How forgetful" Seo sighs and smirks