You know, I read until chapter 6 wondering why the low rating on this one until it was made abundantly clear why. Essentially, the author adds another summoned human from the MC's world to the story. This dude not only is better at everything compared to the MC but he also gets all the pussy. Remember that the very first scene of chapter 1 is the protagonist wondering if his wife is cucking him and now that's pretty much what the friend also does to us, as the reader.
Basically, NTR