Ushijima's father was a second division volleyball player who used to attend Shiratorizawa; his generation is rumored to have won first place at Nationals. However, Ushijima's father had to retire due to an injury and then married Ushijima's mother, taking on her surname in the process. Sometime later, when Ushijima was still very young, his parents divorced and his father moved overseas; Ushijima ended up taking on his mother's last name.

During his childhood, Ushijima's mother wanted to change his left-handedness because it was not something that usually occurred in her side of her family. However, Ushijima's father disagreed and implored her to let him keep it, stating that it could become the child's greatest power.

Ushijima bases his volleyball style now on an encounter with his father back when he was very young. His father told him stories of the ace on his team who gave off a strong feeling of security and strength that boosted the team's morale. Ushijima has stated that he doesn't want to be like his father, but like the ace his father had described. His father'd also told him to join a strong team and meet new people, encounter new abilities, and grow. But no matter what happens in the future, as long as Ushijima likes volleyball, his father will be happy.

Приняв совет отца близко к сердцу, Ушиджима присоединяется к одной из сильнейших волейбольных команд в стране — начинает учиться в Средней Шираторизаве. Уже тогда он стал соперником Оикавы и Иваизуми.

Кроме того, что он ас Старшей Шираторизавы, Ушиджима в то же время один из представителей сборной Японии для Юношеского Чемпионата Мира.