大蔵 衣遠

Resona's full brother and Yuusei's half-brother.

It is revealed later in Otome Riron to Sono Shuuhen -Ecole de Paris- that he is not Ookura Shinsei's true son, and that he was conceived in result of his mother's infidelity, making him an illegitimate heir to the Ookura family. His ambition and obsession toward talent was the result of his insecurity from that.

This also means that he and Resona are half-siblings, and he is not related to Yuusei by blood.