I made enough progress to post some guides.
To able to enter the school, you must met Mei (the schoolgirl that is winking) and talk her twice, one in the entrance of the school (1700 hrs) and then in the parking area where a vending machine is. You'll get a note which is placed in the vending machine where she will say she hangs around in the shrine in the morning. The shrine is unlocked and you must met her early in the morning 0700. There you get to seed her along with getting entrance to the school. But you'll be allowed during 1500/3pm
For the two girls hiding the photo booth aka the yuri couple, you'll need to come back and talk them a several times. I can't say how exactly the trigger for this one, but you'll get the sign once you interact the photo booth to a point you check who is behind it.
After several times of being a troll, both of them will eventually ask you to seed them (3P). Anyway considering the plot in the game, I suspect same-sex relationships are BANNED for an obvious reason and it is why you met this two late at night.
Check purple colored NPCs, they will talk about places in town that will be unlocked, the purple female NPC in the "breeding area" in the clinic will unlock the Pleasure Club (seems to be a PC cafe), the final heart is get in 3PM