So, Hitei translates into denial I believe, and from what I remember on the discussions way back when was that she denied everything about hating Togame and having possibly liked Emonzaemon. Shichika loved Togame and there was no denying that. Togame also planned on killing him without a doubt. This is where I'm a little lost, so feel free to correct me.
Shichika realized that Emonzaemon killed Togame outside of Hitei's motives, given that she doesn't actually hate him. After killing him, what reason does he have to kill Hitei? On the other side, he has every reason to kill the Shogun. By killing him and forgiving Togame, he was able to finally become a human.
The last bit following the credits is actually what I enjoyed the most. Shichika probably doesn't want Hitei following him, but at the same time they basically experienced the same thing and can deal with it. Also, and this may be just me, but I'm pretty sure Hitei was funding Shichika's traveling expenses to draw the world map.