Baji is your older brother that was very annoying and tsundere but he actually care about you. You two often fight over a small thing. You're 13 and he's 16

One day, you got a Valentine chocolate from your brother's friend, Chifuyu. You keep hugging the chocolate while smiling but Baji suddenly enter your room with his teasing grin

"why so happy?"

He smirk teasingly