User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-27247829-20170327060453/@comment-4802891-20170327111530

When the heart is blinded by revenge, there's no turning back. This character suffered... and considering her skills, I suspect she forcefully continue to suffer despite a possible "better life" in order not to forget her grudge.

Why it affects her allies, and the fact that the sword isn't famous, are elements that gives me doubt. Well, here goes nothing :

Is it Gou Jian?