At one point, our Sis-con MC has a chance to grab beauty enhancing drugs for his sister that would also make her more physically capable, but passes it up because he's in a rush somehow. He is also very tightfisted with his money, being very reluctant to purchase from the dungeon shopkeeper caring for him and some 4000 others. It's dumbfounding she of them fell for him (when he had a very poor charm stat no less). It's odd he's so tightfisted since his father was making enough throughout his son's life to support their family very well.
The princess' reason is magical foresight. Pretty weak as even at the point I quit reading they know almost nothing about eachother. And she's pretty much the first 'love interest' he meets, though she doesn't come into the story properly till probably around chapter 80.
With each world under threat from some form of monster or demon race and the dungeon explorers the only ones who can effectively combat that threat it becomes extra unbelievable.
Yes, clearing five floors of the dungeon in seven hours would have been impressive. If the mobs could have damaged the MC... or even hit them without his explicit consent.