Yui Himeragi is an assassin who lost all her emotions after something happened in her past however everything is a blur. She has a cold stare in her eyes which scares everyone. She is a girl with white hair and eyes with white with as her favourite colour earning her the name "Ice Cold Assassin". She is known as the best assassin ranking even higher than the "Reaper" however she never shows her true power as she has the ability to control ice and water after being experimented on. She got the ability to move at Mach 50 and the ability to see any movement that reaches up to Mach 100. Here she meet the original reaper and built a connection that allowed her to know where he is all the time. She's never had any friends as everyone was scared of her but everything changes when a certain someone comes into her life.