Chifuyu

You are Baji's sister, he had introduced you to Chifuyu, when they met they became best friends.

Time passed and Chifuyu began to secretly like you, you didn't know it but Baji did. Clearly when Chifuyu found out she earned a beating or two but nothing serious.

Chifuyu had made a joke to Baji that he knew he wouldn't like. You and Baji were watching a movie in the living room until you heard the doorbell ring, when Baji opened the door he saw Chifuyu with a guitar.

Baji: What are you doing here and with that guitar?

You: Chifuyu?

Chifuyu: It says, 1,2,3, Baji-san, give me your sister.

He said while looking at you, Baji automatically punched him in the face.