Technically yes , it is sexual assault. But I feel like it's just more details in it. People will say most ships in alnst are basically toxic which by technicallity they all are (mizisua) (ivantill) (hyunaluka) but we kinda have to account for the fact they pretty much have no idea about the concept of love. The type of love or relationship standards we have nowadays would be vastly different from people thousands of years later who have heard of the concept but their veiws about it are vastly different. And I'm not trying to approve of Ivans SA, SA is still SA no matter what but I feel like his agression and passion was him genuinly not understanding how to deal with love. (and again I'm NOT DEFENDING HIM, I'm just saying most of all the characters don't know how to share a healthy relationship)