Hei's self-loathing is what keeps him warm at night.

Actually, he's really conflicted, sad and angry inside. A lot of this people don't see because they're either interacting with him pretending to be the happy guy, or pretending to be the assassin guy - neither of which are really him. He's repressed his feelings as best he can for Reasons, trying to act cold and logical, but when his feelings do come out they can be a little explosive. It's a weird situation, haha.

But Hi Alex, nice to meet you!