Why can't Erkang beat Musha?

It should be Erkang's mercy to release Musha on purpose. After all, Musha is a girl, the daughter of the king of Myanmar and the princess of a country, with a special status, which is related to the two countries.

It is also said that Erkang especially appreciates Musha on the battlefield, or he likes him a little, otherwise he will not let Musha go again and again.