I Lent 500 Yen to a Friend. His Sister Came to My House Instead of Borrowing. What Should I Do?

I Lent 500 Yen to a Friend. His Sister Came to My House Instead of Borrowing. What Should I Do?, Yuujin ni 500-en Kashitara Shakkin no Kata ni Imouto wo Yokoshitekita no dakeredo, Ore wa Ittai Dousureba Ii n darou, 500 "Until my brother returns the 500 yen, I will gladly become senpai's property as collateral!" One summer day, Akari Miyamae, his friend's younger sister, came to the apartment of Motomu Shiragi, a university student. What is the secret behind this debt, and what is Akari's purpose? An overly-sweet cohabitation comedy that starts with one coin!