That is a very hard question to answer without giving away too much of the plot.
It takes a while before the love interests (LIs) can enter into a relationship with the MC due to various events. The LIs will come to a place where they agree to the MC dating within their group. The player can choose at various times to go outside the group. Sometimes the LIs will be okay with it, depending on who it is and if they have given the go ahead. The LIs will consider encounters they haven't approved of as cheating and the LIs will not be happy about it. If the LIs lose too many points the player will find themselves rejected and single at the end of the game.
Eventually, the player can ask the LIs to become his harem. The player can then ask for permission to sleep with other women outside of the harem. Their agreement will depend on various things. So it takes a while before the 'official' harem kicks in, but there are times when the MC can enjoy other girls outside the LIs. This game isn't going to be a free for all like many harem games, but there will be more variety as the game progresses.
I hope that's clear enough.