There is nothing suspicious about this. It being 780MB doesn't mean anything, that is likely what it is before install (or without the adult content), GOG installers are compressed.
https://vndb.org/v23772
Also note this one:
https://www.avxdown.com/view/4195968
is the same size as this torrent. There is also the fact the adult content is already included in both this torrent and the one by girlcelly.
Comments - 5
MrLucky_Aim
Anon1
Shaun
Masamune
Shaun