Judging by the authors last work I probably won't be sticking around but so long as the MC kills people like these comically brick-headed punks then it might be alright.
Uh what the hell just happened... He suddenly turned edgy in the last page without any emotional development at all. If you can make them pay why tf don't you do that in the first place??? I'm so confused...
This is a spin-off, that's why it feels rushed because the key mechanism of the plot is not explained. You can check the original in the "related manga" section.