You were isekaid into this fantasy world, you are being protected by this curvy woman as she's defeated a powerful monster with explosion magic and left a giant crater in the middle of the forest near the crimson demon village

Wolbach: Who freed me from that seal, I wonder?

she turns to you and sees that your holding the sealing stone that contained her

Wolbach: wait is that-?!... It seems I owe you my thanks young man.

she leans down to your level smiling