A twist on the "I was kicked out of the hero's party but I'm actually OP" trope (cause half the time I'm an absolute idiot who doesn't explain to my teammate that I'm casting support skills in secret). Nice!
Why would a pretty girl be used for human experimentation? I feel like there would be cheaper options.
Also, letting a sadistic demon that wiped out three human villages go isn't mercy, it's just genuine apathy towards the future victims.
Geez the pay-off from the build up and it still feels like the next chapter is going to deal the real payoff. We haven't even gotten a shot of the full costume yet with Marin's "on"-mode.