The problem with Leon is that he basically this series version of Kazuma, but Kazuma works because Konosuba is a pure comedy and he surrounded with a group of idiots. Leon on the other hand ia with a duke daughter, a commoner (future saint), and sarcastic A.I. his personality doesn't work with this type of story because it plays it very straight shounen and romance/harem story and there some politcs involved, however this story saving graces is his interaction with the otome game villainess and protagonist. His "Im nothing but a Mob" mentality gets really annoying pretty fast because if he accepted that he is a Mob, he wouldn't get Luxion and would have accepted his fate of getting married with his step mother friend, because other boys in academy hate it too, but they accepted because they have no other choice. His knowledge of the Otome game and his decision to get Luxion
and Marie trying pretending to be the "protagonist " is what causes all this world alteration and he just trying to stick with Otome game script is what bites him in the ass, because the alteration have already been done, things can't go to the original story because of these alterations. Leon needs to understand in the future volume of the LN is that he already the HERO of the story rather than the otome games protagonists, he basically an reluctant protagonist with a sarcastic attitude, dense of his action and his relationship with who he interacts with and low self esteem issues because of his experience of his previous life.