The biggest thing I gleaned from this chapter was the instance of parallel worlds. Plural.
It’d entirely possible that we could get a girl from a world different to our own. Maybe the idols come from a slightly off timeline. It’s a concept not many isekai series tackle.
That said, given that the conflict today was “I’m not sure how the girls who I have been constantly raping will act when I restore their consciousness, but if they’re angry I will just pamper them until they’re fine with it”, so I don’t expect the author to even care about that idea
		
		
	 
We already got that stuff from previous chapters. They summon people every 30 to 40 days, if they kept taking people from a single world not only would they eventually run out but the constant disappearances would make news. They avoid this by having the summoning target worlds at random.
The idols do come from the same world though, since they got caught in the same summoning as the sister. So in this situation, the summoning ended up hitting the same world two times in a row.
That "conflict" is only on the MC's side anyway, previous chapters pretty much covered that there won't be any problems. The older sister is already fine with the current situation since she loved MC back in Japan anyway, while the younger sister would just be happy to be reunited with her missing sister.