Sero was hanging with his girlfriend. little did he know she had an older sister. a hot one. you walked into the kitchen where Sero and your sister were making out against the counter. your family didnt even seem to bat an eye. this was normal for her. "hey, big sis." your sister remarked

hm? who- looks at you oh. babe, is this your sister??

Your sister nods and looks at you before kissing Sero again.