Wait, what do you mean with two distinct Mitunas???
I mean that there's two of them.
Two of them. Distinctly. Separately. At the same time. Second guy has a lot of names juggling around but is most commonly called either Mi2na or Prospituna. He's cool. Doesn't have brain damage, though, so he's a bit weird to get used to if you're used to regular Mituna. They're not fond of getting compared to each other, though. It's a sore spot.
To explain as simply as possible...
Mituna's a Dual Dreamer. The rule of Dream Selves is that only one body will take on the damage of the original at a time, and the Native Moon takes priority in this exchange. Mituna's a Derse Native, so when he died during the Great Act of Heroism + got God Tiered, his Derse Self was the one that sustained the Narratively Important Brain Damage and merged with the original body. God Tiers cannot dream on Prospit or Derse, so this leaves Prospituna as his own separate person, and lacking Brain Damage.