Saito bears a surprisingly strong resemblance to Izuku Midoriya, possessing the same wide eyes, a mess of fluffy hair with prominently dark shadows cast over it, as well as a similar physique.
He wore the official uniform of his institute, which consisted of a light-colored dress shirt and tie, as well as a darker blazer.
Not much is known about his personality, but according to the people who knew him, Saito was really popular with everyone at his school. In the only image there is of him he is seen fighting against someone, although the reasons for this are unknown.
Saito attended the same high school as Himiko Toga. Himiko "fell in love" with him after seeing him bleeding because of a fight. This gave rise to the true nature of Himiko, and later she attacked and heavily injured him. Himiko stuck a straw into Saito's body and drank his blood.
It is not clear if Saito survived the injuries.