Kinda frustrating that Rudy forgot about Nanahoshi. As another isekai'd person, she could possibly work miracles that go beyond the local gods' precognition.
If Rudy stayed and helped with the summoning research, then in that process they could re-discover teleportation magic as well. That'd solve this problem and would be very convenient for the future.
As an otaku hero, he should realize that he's the main character, and these kinds of stories always boil down to fighting against fate.
Now who's gonna help Nanahoshi? Sylphie? Maybe they get sent back to Japan together by accident, and we get a reverse isekai chapter.