I've played such jrpg once and it's one of my favourite game, storywise. It's a trilogy called Ar Tonelico.
Most of the gameplay are quite easy jrpg with no challenge whatsoever, but the dating sim aspect is tied to your heroines/waifus' skill tree. Basically, to unlock your waifus' new skills, you need to play an imaginary roleplay dating sim inside their dream to help relieve the mental trauma or insecurities of those waifus. In order to view these dream events, you need to pay DP which is accumulated through battle with that waifu in your team(basically AP but for waifu). Some major event will require you to pick your answer that will result in varied DP pay to finish the event. After that, you'll unlock her new skill. It's more straight forward with little to no branching path so you could say that it's more of a VN than dating sim. Out of the dream world, there are a few branching path in a story that will determine which waifu you'll end up with after you save the world. In Ar tonelico 2 and 3, these few branching path choice can lock you out of the latter part of the dream world of the waifus you didn't choose (latter half for AT2, but quarter half for AT3). Both aspect of gameplay are pretty easy in difficulty anyway. Do check them out. I suggest Ar tonelico 2 because they have some interesting ties between the story and the dream world. Ar tonelico 1 is a more traditional jrpg, but you can pretty much blast through waifus' dream world with enough grinds, unlike 2 and 3 that have story locks. Ar tonelico 3 is called Ar tonelico Qoga in the US by the way and it has heavy fanservice elements and is mostly seen as a bit of a black sheep of the series.
