Oh yeah I forgot you've created this thread back then
One thing that I noticed from the first chapter is that the MC and his friends doesn't need to defeat the demon to make the contract... still, that scene where the demons were eating humans seems to imply that they failed to defeat the demon and that's why they're eating them.
I wonder if they're going to fight them in the next chapter.. or maybe ignore it completely and makes them their demons from get-go.