Itsuki is Aira's 14 year old little brother who usually teases her and is the object of Reina's affection. He is younger than Aira but is more mature and not as clumsy. Itsuki helped her keep the secret about being in the Prism Shows from her dad together with their two younger twin sisters. It looks like he has an interest in doing the family business. Itsuki is studying to be a sports doctor at a young age. (Source: Wikipedia)