Accusations of sexual assault, sexual coercion and rape can happen to anyone. Too often accusations are not taken seriously (because, for example, one is not aware of guilt or the alleged crime occurred a long time ago). A criminal assault can occur without any violence or coercion (even rape does not legally require violence).
Even without a “no”, the behavior can be punishable, as it is supposed to depend solely on the (often ambivalent or not clearly expressed) will of the other person. Despite usually thin evidence (word against word) and frequent false accusations, sex against an alleged opposing will can result in several years in prison (without parole).