I would like to preface this by saying that as of now I have only seen season 1+2 of the anime + the movie so idk if the writing changes much or if he is written differently in the manga.
When watching konosuba it feels like Kazuma acts almost as 2 different characters, most of the time he is a decent character who while not a great guy is kinda likeable and is a pretty good protagonist but in certain scenes and episodes (like the succubus one or his interactions sleeping with megumin in the movie) he is written in an excessively perverse and predatory way that i struggle to see how it helps him as a character.
his comments about age and how long the succubus can go just feel gross, they don’t create humor, they just make him super unlikeable and unbelieviable as a character.
idk if I’m missing anything but the scenes where he suddenly becomes super perverse just feel unnecessary and actively hinder both the believability of the world and the likeability of him as a character.