walkthrough, quick version: mom vaccum 5 times in first 2-3 days, skip school using bed until teacher housecall. Next schoolday after teacher unlocked, go home early in the last 30min of the time block. when transfer shows up, talk to her for 2 days, then go home early if you have at least 300 on all other girls and "cooperate". On day 17, control transfer student after school and enter under the plaza arch at 16:35. check the ally on the right for secret walls. Good end achieved.
Good end has an advanced ending, and it is all the remaining days are used for. By having Vaginal sex on the correct days in all 4 time blocks for all 5 girls, the ending "upgrades" to involve pregnancy.
Doc on 22, teacher on 24, sis on 25, mom on 26, transfer on 29.
Walkthrough I found in the comments. You'll want to use it to find everything because content is super easy to miss in that game.