Yuujin ni 500 Yen Kashitara Shakkin no Kata ni Imouto wo Yokoshitekita no Dakeredo, Ore wa Ittai Dou Sureba Iin Darou is a Manga/Manhwa/Manhua in english language, SUGGESTIVE series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

"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!