I'm a librarian who loves anime, manga, and reading a wide variety of genres.
The author is pretty clearly a guy, based on the mentions of boob size of each of the female characters, and the one female character whose breasts are apparently so huge that the male characters can't help but stare. -_-
The setup feels like a JRPG. The world is in danger of being taken over by a demon lord, so a group of humans summoned a hero from another world. Summoned heroes always start off low level, so that's expected. However, the hero's companions are supposed to be capable, and they totally aren't. One's a level 10, one's 15, and one's 20, which apparently translates to "novice or worse." The group's only powerful member is the priest (the group's healer). Readers haven't been told his level yet, but he's apparently so powerful that he's worried the others might use him as a crutch, so he lied and told them his level was 3, the last digit of his true level. The grumpy healer aspect reminds me a little of the game Healer's Quest.