SSS-Class Suicide Hunter

His master was not a perfect person.

[That's not how you do it. Watch closely.]

There was always a slight thrill mixed into those words.

[You're doing well. Quite impressive.]

There was always a slight jealousy mixed into those words.

[At this part, there's nothing more I can teach. You're better than me now. ]

There was always a slight frustration mixed into those words.

The reason he could feel these emotions was not solely because he was particularly perceptive. It was because his master did not try to hide them.

When he first became a disciple, his master clearly said:

[I will treat you as you are.]

[....]