Aah, I see, I see. You just have to get him in.. a mood. He's like a stubborn woman when you're ready to go and she just isn't feeling it.
It doesn't require a candlelight dinner, nono— don't worry.. but fight with him sometime.

See what happens when you almost kill him if you haven't already.
_{[ Like Gintoki found himself doing... it's a pity that guy is immortal. ]}