Шішіо Цукаса

According to Taiju, Tsukasa has the reputation as "The Strongest High School Primate" due to his tremendous fighting abilities.

Tsukasa is essentially violent, but extremely careful and aware of his actions. He is a very kind, thoughtful, and polite man outside of his pessimistic ideals towards humanity. He offers help in the beginning to Senku and Taiju after they revive him and becomes their hunter for food, using his skills as a prominent athlete to aid them. It’s revealed later that Tsukasa plans to purge humanity of adults who hurt the young and weak, then thinks Senku will go along with him, but instead Senku rejects him. After this point, Tsukasa becomes fairly determined in carrying out his plans even to the point of leaving their group.