I can't remember for sure, but this sounds like Kira's sunbathing quest. If it is this starts at 12:00 and you have to catch Kira sunbathing (not with Kira and Ann) it will progress from there to rubbing lotion then to 2 or 3 differnt sex scenes.
Nah, I've done all of the Kira sunbathing stuff from 12:00 (both alone and with Ann) until it keeps repeating, it's the same quest and same step but a different objective (the one you're talking about is Kira's lunch breaks).
This line seems to indicate that I must apply lotion to Alice when she's on a towel next to the swimming pool from 13:00 to 14:00 (often bra-less or naked) but I've reached a point where she doesnt do that anymore. I'm not sure if it's because Ann is now home and cleaning rooms during that time or if it's because I joined the college... I wish there had been some sort of safety to prevent this from happening.
What's also weird is that I somehow joined the college in between the two medical examinations that seem to be prerequite. (But i don't read most dialogue so I'm not sure if that's normal). Overall it feels like the storylines are messed up around that point.