Well... I think the overall idea is to get her comes comfortable with MC, the more is revealed the better, i remember that soon after she get more open we can follow her story, but i remember that i could only achieve that after ending all paths, at that moment the only one it was active was Asami's one, so, soon after it was closed and sleep with Yasuka it was activated Yasuka's path. But in that whole time i spend all night with her, iirc, it's needed to spend at least 10 nights, but i think there was more than just that...