He is a student of Kunugigaoka Junior High School. He is assigned to Class 3-E, where he trains to become a professional assassin, with his teacher as the target. His partners are Takuya Muramatsu and Taiji Yoshida.

Terasaka is a rash, selfish and impatient individual. Desperate to escape from the miserable circumstances of being part of the dropout class, he is willing to resort to any means, even if the methods may be immoral.He holds no regards for the injuries of his comrades who provide assistance.

However, Terasaka possesses relative leadership skills, as he is usually accompanied by his peers, Takuya Muramatsu and Taiji Yoshida.He persuades others to do his bidding by being direct and intrusively forward, as indicated when he pressures Nagisa Shiota to carry out an assassination of Korosensei by reminding him of the harsh conditions they live in.