Seems like a fluffy version of Hige Wo Soru from what I'm hearing about it.
Just happened across the manga for this while randomly browsing and started reading. Starting from chapter 2, I don't think 'fluffy' is exactly the description that first comes to mind...
This one has a manga adaptation now. I am 10 chapters into web novel and its pretty nice. So far it has not been like super smutty. Adult yes, but the adult act is not the main purpose of the writing but more like a cherry on top of a cake.
From what I understand the LN stripped out the graphic sex description leaving it just ecchi compared to the original WN.
You have been misinformed. The WN also fades to black at the beginning of sex scenes; only the bath scenes are present. 異世界迷宮で奴隷ハーレムを is published on the all-ages side of syosetu, not the R18 side.