YUUJIN NI 500-EN KASHITARA SHAKKIN NO KATA NI IMOUTO WO YOKOSHITEKITA NO DAKEREDO, ORE WA ITTAI DOU SUREBA IIN DAROU

"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) — Description from AniList community (anilist.co).