Why didn't they go back and get crystals? On the other hand, considering how much of the cave they went through, why didn't they see any? Feels a like the author wanted the humorous ending, but didn't bother making it justifiable. Especially considering that Kuro has been adventuring in that cave for quite a while now, and no mention of hordes of goblins. Also, he doesn't have much money, ex-assasin, why no looting?