You technically can, but up to certain points in the story. The way the game is designed is that the story is intertwined with the relationships you have with the cast of supporting characters, and at certain points only being able to progress once you either fulfill a main storyline event while keeping up with the whole relationship mechanic. I'm not entirely sure, but you *could* avoid most of the game and not give a shit about everyone else, and you'd be fine. You'd cripple your stats and gear to a certain point, but eh, it's an option. Again, not sure cuz the game intertwined those two aspects very closely, and I can't remember if meeting some relationship criteria is mandatory to progress the story.
...it probably is. Maybe.
Also, for the replayable scenes, don't wanna spoil it, but one of the first characters you meet will give you an item to watch all scenes, SFW or not. It'll be long ways tho, if you only started.
