Setsuna Kashiwagi

Setsuna Kashiwagi (柏木 セツナ Kashiwagi Setsuna) is a high school student in the care of his older sister Mirei Kashiwagi ever since their parents died. Setsuna was born with a weak heart and has been the victim of bullying through most of his life. Overhearing a conversation between his sister and loan sharks, he feels that his life has been just a burden to his sister and decides to commit suicide. Literally on the edge of the bridge, he is confronted by a mysterious man known as the "Middleman". Middleman offers him 10 million yen to postpone his suicide by one year. After Setsuna accepts, he drinks "Banrikou" as proof of their contract. He wakes up the next morning, thinking it was all a dream until he sees two girls sitting beside him. They introduce themselves as Kanna and Rena, princess sisters from the Oni clan. They explain further that because his Banrikou heart now gives off a scent that attracts demons, they have been sent to protect him until his heart fully matures. If he is attacked by a demon, Setsuna will be able to summon one of the sisters, whomever one he thinks of the most. At the end of the year, once his heart has fully matured, the sister Setsuna summoned the most will consume his heart to obtain the ultimate form. Ever since Setsuna drank Banrikou, his heart problems have disappeared.

Though an introvert, Setsuna has a caring side that surfaces occasionally. He has shown considerable bravery for the sake of protecting the ones close to him.

It is unclear who Setsuna has feelings for. He has shown interest in Kanna, Rena, and Arima. With recent events at the hot springs, it is hinted that Setsuna may have stronger feelings for Kanna although it could just be admiration.