Tsukishima was a lot more cheerful when he was younger and had a very close relationship with his older brother, Akiteru Tsukishima. As a young child, Tsukishima seemed to really like volleyball, arguably due to his older brother’s own love for the sport. However, Tsukishima’s attitude towards volleyball (and club activities, in general) changed when Akiteru entered high school and became a member of the Karasuno High Volleyball Club.
Despite practicing very hard, Akiteru failed to become a regular player for Karasuno due to the number of more talented players on the team, including Hinata’s idol, the “Small Giant.” Seeing his older brother’s disappointment, Tsukishima began to think that he shouldn’t put so much effort anymore, like his brother did, to avoid being disappointed if he fails.
Sometime in elementary school, he sees Tadashi Yamaguchi being bullied. He doesn't do anything, except call them pathetic. This was aimed at both Yamaguchi and the bullies. After seeing how Tsukishima could stand up to the people bullying so easily, Yamaguchi starts to look up to him.