星月 恵那

Ena is Souma's younger sister, unlike him, she is very popular with the opposite sex and often brings men to her room. Her parents don't suspect her true nature and think she has a boyfriend but she makes them believe that "he is just a friend, nothing more". She already had, at least, 3 "boyfriends" (= sex friends).

She doesn't seem to care who can be her partner (before having sex with her brother). 

When her brother interrupted her, she decided to take revenge by raping him. She immediately found their compatibility "excellent", telling him immediately that it was the first time she felt so good. Since, she becomes aware of her brother as a member of the opposite sex and tries to seduce him sexually.

Later, she becomes aware of her deep feelings and finally start to seduce him seriously so that he can become her boyfriend and she no longer seeks to see other boys. But because Souma is very dishonest with his feelings, she decides to lie to her brother in order to make him explode of rage while going out with her former Sex Friend on the day of the festival in order to force her brother to confess his true feelings.

She is very clever and knows her brother very well, she knows that only jealousy will make him say his true feelings and that to have more control over him, to let him fertilize her and to promise him a child./