I like the humor thus far but regarding the exposition dump, I think a better way to have handled this would have been to start with him already enrolled in the academy. Then the students could have gossiped about the death of the demon lord and obviously credited the hero, but just have him internally monologue/flashback on what really happened and why he's there now. The politics involving the hero and their country, ect. could have been handled by a teacher in a history class or some shit.
Most fantasy manga will spoon-feed you info to get the protagonist power-up number eight and harem member number six, so I'm not disappointed, but there are certainly more elegant ways of avoiding the narrative conceit of two people lecturing the other on information they both know.