Of course you can play it however you want, manslut or otherwise. Buuuut...
Personally I think it's more fun to stick with a consistent personality when making MC's choices - unlike many other games, you actually get real consequences from your choices. It's a lot of fun to watch how it all turns out.
There are several quite different experiences available, depending if you are a "normie", a "sub, or even if you are brave enough to go the Kim routes... enough difference to the story that it makes sense to replay with different choices...
And you also have the chance to use the "Scenarios" function to follow the core sections of different character's paths along each available route (dom, sub, romance) which of course includes all sex scenes, without having to go through the rest of the story every time.
Finally, speaking to the "manslut" aspect... it may have all been "fun and games" up to chapter 6, and players could mess around with almost all the characters regardless of commitment or expectation of monogamy... but the reckoning is coming... by gawd, it do be coming!