Aruto has always interested me, and after reading chapter 47 I became a total fangirl. XD
Aruto Tsukiyomi (ćčŠ ćć)
He is a prominent japanese violinist who was once known as a genius. He is also biological father to Ikuto and Utau. 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.
Aruto is very similar to Ikuto in both looks, attitude, etc. Also, appearently, when Aruto "disappeared" he had a plan with Souko to stay together. In chapter 43 Souko reveals she had never re-married to the Easter director.