We know xp necessary increases per level up.
When he was level 26 he got 1558 xp and leveled up to 33 that's 7 times. Even if we're generous and split it even that approx 222 per level up...that doesn't make sense when before that he got 150 xp for a gargoyle and said it wouldn't be enough if he kept hunting there... Cause even then it'd just take 2 gargoyles....they really flubbing the math
I don’t think that they thought we would pay attention to small details because during the fight with the ogre his sister and her team cut the monsters arm, the monster also fought back a lot. When they showed the monsters MP and HP it was entirely full, even with his arm being cut off. Also he constantly fought monsters 2-3x his level and it would only be enough to level him up 7 times, at the maximum.
But he might be a summon so I'm still holding off. He reminds me of that guy that worships Thanatos in that other comic. WHOOOO and smashes his head against stuff? Idr the name.