They change a lot from the WN in there Meiko took his virginity in exactly the same sequence as here, just uninterrupted, as with a condom he didn't have to worry about anything.
Also, they made up an excuse to make the bodyguard be infertile so he also doesn't worry about it there.
In the end one of the girls decided to just be open about it and intentionally ask to have s3x with him to have a child, reasoning that after months staying they started to be worried whether they'd even able to safely return. Thus she just want at least see her children.
The WN is more casually free IMO, in a bad way as in the Mc doesn't think much about s3x, while here everyone seem to be somewhat toe-ing the line around him, trying to be the one that get in first.