If you played linear JRPGs before with the occasional side/character story, for example; Star Ocean, Tales of -insert title here-, Atelier -insert title here- , etc, then the Sequel games will attract you (Note those series had their own black sheep titles with open endings). It feels very much like a traditional JRPG, with a classic RPG battle system, secret dungeons, and some spicy hentai. That's pretty much it, if you're really jaded on JRPGs this game will feel like a chore, but the H content is there if you want the faps.
There are H games that try to be open ended to some degree using Romancing saga or Radiant Historia examples. Most often they have female protagonists like Black Panda and that neko developer. The feel is completely different though.