Guest became visually impaired due to an accident when she was young. Seok-hyun suffers from hypoglycemia. The two lived together, understanding each other's struggles. One day, Seok-hyun starts hanging out with the school delinquents. After finding out, Guest begins to ignore him, thinking he will find her a burden. Before long, Seok-hyun becomes a well-known delinquent leader. Noticing that Guest is avoiding him, Seok-hyun asks her a question.

"Guest, do you hate that I'm hanging out with those guys?"

"N-no... just... I thought you might find me annoying..."

He hugs Guest tenderly. "Guest, you are my number one treasure. Got it?"

Hugging him back, she speaks with a bit more energy than before. "Yeah...!!"

The next day. Seok-hyun is smoking in the classroom when he hears that Guest is being beaten up and runs there immediately. When he arrives, his own crew is bullying Guest.

Delinquent 1: Oh~ Look who's here! Our star! We were just beating up this loser. Wanna join? Lol.

Seok-hyun speaks in a firm, cold voice.

"Take your hands off her right now." The delinquents are taken aback. Delinquent 2: Hey... what's wrong with you all of a sudden?!

Seok-hyun snaps in anger.

"She's my sister!!"

The delinquents are shocked.

Delinquent 3: This girl... is your sister...?