Kei Tsukishima enters Karasuno High's volleyball team with aloof cynicism and minimal enthusiasm. This detachment originates from childhood disillusionment after witnessing his older brother Akiteru's failure to become a regular player despite intense effort, a failure concealed through deception. This betrayal eroded Tsukishima's trust in passionate commitment, leading him to view volleyball only as a casual club activity to avoid similar disappointment. Standing 190.1 cm tall, Tsukishima leverages his height and analytical mind primarily for blocking, excelling at reading opponents' strategies and executing feints with precision timing. Despite his skill, he maintains low self-esteem, openly acknowledging inferiority to teammates like Hinata and downplaying his achievements after critical plays. His interactions are marked by sarcasm and provocations, especially toward enthusiastic players such as Hinata and Kageyama, though he shows deference to senior teammates. He shares a steadfast friendship with Tadashi Yamaguchi, whom he defended from bullies in elementary school. Tsukishima's evolution begins during a Tokyo training camp, challenged by Bokuto's mentorship and Yamaguchi's confrontations about his apathy. This shift culminates in the Shiratorizawa match, where successfully blocking ace spiker Ushijima Wakatoshi ignites his latent passion for volleyball. The victory validates his abilities and fosters a deeper connection with the team, though he initially struggles to express this newfound motivation openly. Following this breakthrough, Tsukishima adopts a more dedicated approach, intensifying training and strategically refining his blocking techniques. He practices with collegiate players to sharpen timing and studies opponents more rigorously, evolving into Karasuno's "rational mind" on the court. His commitment endures beyond high school as he balances collegiate studies with playing middle blocker for the V.League Division 2 team Sendai Frogs. Post-graduation, he plans to work at the Sendai City Museum, indicating a dual focus on intellectual and athletic pursuits. Notable personal traits include a preference for strawberry shortcake, an interest in dinosaurs evidenced by figurines in his room, and a thematic association with the moon—reflected in his surname's kanji and childhood apparel. His given name, "Kei," translates to "firefly," alluding to a self-sufficient light contrasting Hinata's sun-like symbolism.