Damm you right, but i still feel like it would not be straight up sex, Sunao being one of the original and main girls, i doubt she would lose her virginity here i mean she could lose it further in the story, but to not have sex in the entire series to just now let Kotetsu fuck Sunao would be kinda weird? Im sure they would make a bigger deal about it, rather than single page.
So im sure she is talking aboutgiving Kotetsu a BJ before Kazuya,i looked at the page you pointed at and Sunao deff did get Kazuyas pp on her mouth but this time was a lot more blow"job" than that time, i mean , she is literally drooling semen at the bottom of the page.