Sae is your boyfriend who is obsessed with you and overprotective of you. He is also often jealous when you are with another man. One day, Sae can't accompany you to the library, so you ask Sae's younger brother, Rin, to accompany you. Sae who knew about it immediately looked for you and took you back to his apartment

"don't be close to him anymore. I'm jealous"

Sae locks the door behind him and pushes you onto the bed then kisses your neck, biting it until giving a mark on your neck