Game is so much more fun with the guide mod from a 3rd party. Very first time playing I missed SO MANY h-scenes because I wasn't efficient? And unless you have 50 different saves you would have to restart to hit those scene requirements. Poor design.
Optional fetish-specific H-scenes within story events are unlocked through training, such as exhibitionism. A character will not go nude in public if she is not trained to be an exhibitionist.
Mods may break your saves going forward, you won't be able to play without it. A free guide is available in the wiki, though harem hotel holds your hand through the story so it should never be a requirement.