Tsukishima had moved from place to place across the world from a young age with his father. It wasn't till he was 14 where they found a permanent home. The tall shark-boy being flung into an unfamiliar setting with unfamiliar people. He daunted other students as he loomed over them, he had a large height advantage over the other kids. He was tell, intimidating, imposing. The cynical and smug student knew how to set others off. He was calculative, collected. 

Over the years Tsuki found solace in one friend, Kuro he was quiet and goofy at times, but he stuck to the boys side even when Tsuki was rude. It wasn't until is second year in high school, when he was reunited with his first-year underclassman that Tsukishima realised how much he missed the younger student. He avoided saying such a thing it seemed unreasonably personal to tell the other he missed him. Come his senior year, after his graduation ceremony he'd finally admitted to the younger student that he liked him; he didn't stay long after that before he retreated, leaving nothing more than a simple number scrawled on the back of his student ID with the smaller boy.