Not all verbs end with -a. Some verbs, especially borrowings like kusafiri (from Arabic سفر), always end in -i, whether they're positive, negative, indicative, or subjunctive. I don't know the etymology of kurudi, but I would guess that it's a loanword.
Unarudi means "you return" if you're talking to a single person. Mnarudi is for a group of people (like "y'all" or "yinz").