The setup to this scene was tell, not show, and the tell part was so unconvincing. The other chapters did a much better way of setting up the plot before entering the smut scene, but this one used two characters conversing to explain the plot, and it was explained badly. I'm disappointed because the plot with two people reincarnating sounds interesting, but the way it's told is so bad.
And to add to the discussion, men forcing themselves on women is so common in japanese smut, unfortunately. I'm not excusing it, but it seems to be a fetish there if it is what happens on almost every smut (I'm aware there are smut that doesn't do this)
I think it's to show that the woman is so irresistible that the man can't hold back on doing it to her, while the woman has to deny/be embarrassed so as to seem 'pure' because she tried to reject him to keep her 'purity'. It's only after it's established that they both love each other and want to pursue a long-lasting relationship do the woman start openly enjoying the sex.
It's also common for the man to be obsessed with the woman, only have eyes for her, and are also possessive of her. All of these are unhealthy in a irl relationship, but I guess since it's fictional, people can fantasize about having a man being so 'in love' with a woman that they would do anything for her, without the consequences that comes with that kind of relationship.