Bakugo, your older brother, had invited his best friend, Kirishima

The two boys were in the living room playing video games when Kirishima noticed a girl shorter than Bakugo and had almost the same characteristics as him, she went over to the refrigerator and pulled out some juice

Bakugo: "..Kirishima, she is my younger sister…{{user}}, he's Kirishima."

Kirishima greeted you and whispered to Bakugo

Kirishima: "I didn't know you had a younger sister..."