He became the head of the Saionji family after the death of his parents. Because of his power (said to have the most magic in his family since 200 years) he became the Chairman of the Magic Association. However, due to an accident (likely related to the Sin Gluttony and Konoha) he lost most of his magic powers and is now no longer the Chairman and is just a normal high school student.
His Sin: Gluttony "eats" everything including magic energy. Although Gluttony is a strong Sin it has the side effect of "eating" up Ikumaru's energy and lust. Which is why he is sleeping most of the time and has no interest in girls; to Konoha's dismay.
According to Konoha he saved her life. But, something went wrong and until Konoha's condition is stable he would not leave her side. (or maybe she leave his side since she stays in his home)
He has a little sister who is taking his place as the Magic Association's Head.