probably the text explains it. Maybe Reimu is too tight for Remi or soemthing, you never know... especially when Remi's piece is as thick as her arm, she must be surprised
ReimuHm hm ♪
This incident is pretty easy to resolve!
Okay, Remilia! ♥
I'm gonna wring you out to the very last drop! ♥RemiW-!? Wait a second, Reimu!
If you s... squeeze like that...!!
I'll come... I'll blow my load again...!
Uses the wrong kanji in Reimu's name. 麗夢, should be 霊夢.