友人に500円貸したら借金のカタに妹をよこしてきたのだけれど、俺は一体どうすればいいんだろう

"Until my brother repays this 500-yen debt, 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! (Source: ComicWalker, translated)