User blog comment:Hielmiez/Aikatsu Friends! Next Aikatsu series?/@comment-26426093-20180101145517/@comment-5885873-20180111173636

For Rainbow Live, it was in a way confirmed that it's the same universe just many years in future by subtle hints like in Sevendays Love Sevendays Friend the windows contain multiple jumps from last 2 series and there's something about the winged statue that I don't remember due to watching the series a long time ago. PriPara is something of an alternate universe due to the fact that all main protagonists are the same age and they formed a unit together and the fact that Mia's last name changed in PriPara

As for Aikatsu, I think they are either in same universe different places and they don't meet usually as shown by the first crossover episode or it also takes place years in future and for some reason the old idols were allowed to meet new idols as shown in second crossover episode with the magical fog transporting them. In the first crossover episode it was just old S4 using Stars Aikatsu system in Aikatsu Stars world while in second it was Soleil using old Aikatsu system because our main gang just travelled to old Aikatsu world and Yume didn't use the card scanning thing while performing in old Aikatsu world