Yuujin ni 500 Yen Kashitara Shakkin no Kata ni Imouto wo Yok...

"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 thi...