[@LetMeDoStuff]

Perhaps someone else wealthy or influential from the NSF, doesn't have to be the Prime Minister, went against regulations and hired Donny as an extreme measure. Perhaps someone they loved got killed in the conflict, thus they turned to a less legal option and sought out the world's best killer-for-hire? That'd work I reckon. In this case Donny would be completely undercover, having to make sure neither side finds him out.

Plotwise, it'd probably be his mission to murder all the top ranking fellas in Jinrai, as well as any significant threats that stand in his way. It would also just be Donny alone, he prefers working by himself you see.