It really is inception huh
So Ouka was hit by that fatal flaw of the bullet and the real her is in a coma. MC taking it upon herself to fetch the bullet herself and revive her
It's more complicated than that. Ouka tried to commit suicide IRL, failed and found herself in her liminal dream world. Then the dream self repeated her suicidal act, only to fail again, fall into another coma, and wake up in another dreamscape within the head of her previous dream body. And this repeats constantly. However, Ouka is not actually trying to die for real: She's in complete control, but the Suicide Parabellum keeps misfiring.