Ah, this was drawn very tasteful, I really like it.
To all those who are questioning Eris' motivation, let me just say this: By the time she finishes her powerup and decides to return to Rudi, she mostly forgets how to read and write.
That's how simple-minded she is. Simple-minded as in she is going straight to the direction she wants in life, disregarding anything else, not simple-minded as in "dumb". She does not feel the need to tell Rudi in lenght why she is going away, because she thinks Rudi thinks of her as a hindrance (in battles, like with Orsted). Rudi is the opposite, he is overthinking everything. I mean c'mon, you know when you satisfied a girl, dont you? She falls asleep and doesnt have energy to talk. Lol.
Dumb? Definitely. A plot device to break them apart after probably the most important part of their lives were spent together (so basically no one else would have a chance at the moment) so the other 2 trash tier loli waifus can join the harem too? Definitely.
But oh boy, her Intermissions will be FUCKING great, and her return will be satisfying after the initial awkwardness wears off (as in, awkwardness in the story). Totally worth to wait from the end of the 6th Volume until the middle of the 16th Volume.
@Bloodnoise His "low level stone spell" damaged Orsted, who is... lets just phrase it "he is really strong". At the age of 13 (or 14?) iirc. So no, his low level stone spells are already at Saint or King level.
The rankings are for each school (both magic or martial arts), mind you: Beginner, Intermediate, Advanced, King, Saint, Emperor, God.
So our MC is definitely not weak, but his common sense is from his previous life, so he is really useless when measuring other's or his own strenght. Wait and read the next few chapters, I think we will be shown just how deep this difference in common sense really is.
However, you asked whether this is a turning point or not. It definitely is a turning point. Paul said he is looking for Zenith at the South, on the Desert Continent, so after Rudi "regains his sanity", he decides to look for Zenith in a direction different from Paul. That's what you have seen at the end.