Aruto Tsukiyomi

He is a prominent japanese violinist who was once known as a genius. He is also biological father to Ikuto and Utau Hoshina. His marriage with Souko Hoshina was met with strong rejection, because at that time he had no reputation. To allow the marriage, he agreed to the condition to stop pursuing music and to succeed the Easter Company, but the promise was broken when the former chairman, grandfather of Ikuto and Utau, died. He disappeared overnight. After that Souko, Ikuto and Utau came under severe criticism, making them strong characters. Years later his favorite violin which he brought with him appeared overseas. His whereabouts are still unknown. Source: shugochara.wikia.com