@hydrocurry
If you consider working together to be friendship? then yes.
It's stated pretty clearly that the reason the MC won was that he had "friends" to back him up, While the demon king did not.
Again it's not like one of those cringe moments in manga/ anime where the MC gets a power boost out of nowhere, it was just the fact the MC had more people...
So yeah...
Does teamwork count as friendship? I would say yes, but on the other hand, I don´t want to because people get super butthurt as soon as they hear the words " power of friendship" regardless of meaning.