Ranma, since we hate you, we're going to use some manner of ancient artifact to send you to an alternate dimension. Oh, and you'll also be five years old.

(They DO, and when he arrives Ranma KILLS a whole bunch of RAIDERS)

You seem like a nice kid. Wanna learn how to punch people so hard their heads explode?

Eh. Okay.

(They TRAIN for ten years, culminating in Ranma KILLING Kenshiro)

Even though I hate everyone there for reasons that aren't too clear, I'd better go back to Nerima now and save everybody from some sort of ancient evil the Musk unleashed.

(Ranma PUNCHES several people and/or monsters. Their heads EXPLODE)