Hinana Hatsushima

Hinana is Kanae and Manako's sister. Kanae having married the MC's father, that makes her his stepsister. She is the youngest among the three sisters and was still attending school before they were brought to another world. She is also the only one (in addition to the MC) who knew the MC's secrets, which are im marrying rich women for money, and that he didn't truly love Kanae.