So a little explanation here, since there's a rough patch. In the LN when Haruka went to the peddler to buy dungeon stuff, one of the things he was gonna buy was a "Ring of Pheromones" which would "increase affinity with the opposite sex."
Instead of the Class President bumping him and accidentally merging the gear, he just refused to stop haggling until midnight, flat out telling the merchant that "I can keep going all night" to get a discount. IIRC the Class President showed up around then and forced him to give up the ring to bring it down to a proper price. He talks about wanting that darned ring every time things are rough with the girls in his class from then on out.
So his stated goal in dungeon diving is to get one of those rings to make him more appealing to the girls in his class. (And the class president's stated goal is to make sure he never gets one of those rings.)
In the Novel, the Class President is fleshed out a lot more -- she's more of a team mom than anything else, keeping everyone together. And Haruka is uh... insane. Completely oblivious as to how much chaos he causes just running around each day. You're kinda seeing that at the end of this chapter, as he's just idly soloing an Orc King's army and his only comment is "There's just a few too many orcs for this to be called just a few orcs."
Edit: For an example of the insanity, it was recently revealed those mushrooms he's eating and making potions out of and all that?
You know in Dragon Quest games there's stuff like the Seed of Strength that gives you a permanent stat boost? Yeah, those mushrooms are the same thing. He keeps finding them because of his stupidly powerful luck, but they're actually priceless endgame superitems.
And he's using them to make stir fry and healing potion soup.