High school student. 15 years old

This is Haruka, my little sister. We both live with our parents in Iwami, Tottori prefecture, and she's quite a tomboy.
Our house is pretty close to the sea and it's a pretty hot place, so lately, whenever she's home, my sister spends most of her time dressed only in a sports shirt.
-"Haruka! Do you have no shame? At least put on some panties"
-"Onii-chan! Don't be a pain... this is a promotion match and I'm about to beat this asshole up"
(( Damm! Haruka, please stop teasing your brother... You have no idea how much I'd like to slam that tanned ass of yours right now ))