User blog comment:Crimson Storm Mich/Future Units Preview v2/@comment-27268294-20170302024154/@comment-30373133-20170307032205

Basically, Shusui is Shura. Shura sparred with Hisui (his senpai) and Shura won. Well he ended up accidentally killing Hisui though. So after that Shura absorbed Hisui (probably just his power, idek) and changed his name to Shusui because Hisui is now a part of him now.


 * 1) bromance