He and Ryuya are close friends since they are always seen together and seem to be close to each other. Ringo is usually fond of making fun of Ryuya.
Mori Haruki is Ringo and Ryuya's composer. Ringo's original composer was unable to write songs for him because he he didn't know whether to write for his female or male counterpart. Ringo managed to catch Shining Saotome in a trap and demanded that Haruki became his composer too. In the game, it's revealed Ryuya quit being an idol and singer because he blamed himself for Haruki's death. Haruki died from being hit by a car when he went back to get Ryuya's forgotten good luck charm before one of Ryuya's singing events three years ago. Ryuya and Ringo visit Haruki's grave alongside Nanami Haruka at the end of Sweet Serenade.