Tsukishima possesses long light brown hair, typically tied in a ponytail, and light green eyes. Standing approximately 175 cm (5'9"), his physique transitioned from childhood slenderness, caused by frail health, to a more toned build in adulthood. Childhood illness led to significant social isolation until Kuroda invited him to play with other children, including Seya, forging a lasting bond among the trio that endured despite occasional friction, particularly with Tsukishima and Kuroda. As an adult, Tsukishima became a minister within a clan branded rebels after Edo's fall, appointed due to familial lineage rather than perceived capability, fueling his self-doubt. He commanded the clan's defenses during an Edo attack. Following their defeat, clan tradition demanded ritual suicide (*seppuku*) by a minister to appease enemies and prevent extermination. With other ministers dead, this duty fell to Tsukishima; his act spared the clan. Tsukishima's relationship with Kuroda featured complex dynamics and confrontational banter, where Tsukishima would jokingly tell Kuroda to "kill himself" – a phrase gaining tragic weight given Tsukishima's fate. On the night before the ritual, Kuroda confronted Tsukishima as he prepared in ceremonial robes. Their initial argument, where Kuroda accused him of taking an easy escape, escalated before giving way to a mutual confession of love. They shared an intimate final night. At dawn, Tsukishima departed to fulfill his duty, leaving Kuroda behind. After Tsukishima's death, Kuroda created the first Hybrid Child prototype modeled after Tsukishima's childhood appearance. Years later, this prototype exhibited behaviors mirroring Tsukishima, such as offering cherry blossoms – a gesture identical to Tsukishima's past actions, implying his enduring influence on Kuroda's emotions and creations. The cherry blossom motif symbolized Tsukishima's brief, impactful life. His legacy is defined by quiet resolve in duty-bound sacrifice, profound but unspoken love, and an enduring presence shaping the creation of the Hybrid Children.