Student of A Class, he’s the scion to the Hijirikawa family. He seems to have some form of rivalry going on with Ren, whom he shares a room with. He plays the piano.
Several years ago on a snowy day while Masato was troubled and in despair over the pressure of becoming his family’s heir he happened on a girl singing with a group of children. He was so touched by her simple and pure act that he was inspired to pursue a career as an idol. With some difficulty, he convinced his father to let him enter Saotome academy, however in exchange he could only attend for a year and had to take over the family business afterwards. Later it is revealed that the girl he met singing on that snowy day was in fact Haruka.
He dislikes Ren partly because he is jealous of his “freedom” (Ren being the 3rd son of the Jinguuji family, thus not needing to be pressured to take over the family business)