It is possible to avoid non-consensual sex. Choices are fairly straightforward about which will lead to the protagonist forcing girls to have sex. It's a little more complex if you also don't want the girls initiating sex without the protagonist's consent, but it's uncommon. The worst "unavoidable" scene I can think of is one where a girl trips and "accidentally" kisses the protagonist without consent. Anything worse than that is dependent on player choices.