OK guys, so here is what I understood from this game (almost unlocked everything)
First, the five [stats]:
-The first is your health. If it falls to zero, you'll fell ill and lose a day, except if you have a yellow drink (it will be consumed automatically).
If you are sick and your girlfriend loves you enough, she'll come and give you a nice blowjob.
-the second is your frustration. It builds up when you don't have sex and goes down when you do. If it maxes out, you'll have a wet dream and it'll fall back to zero. If it's too high (8-9) you'll be too excited to have good sex. If it's too low, you'll have a hard time getting it up. Ideally you shoud keep it around 5-7.
-third is... I dunno really, but it goes up if you have sex regularly.
-fourth is HER love towards you. Visit her and go on dates to keep it up. If it falls too low, you'll have to shower her with presents to get her back.
-five is her ecchi level. It goes up when you perform particular actions when the third stat is high enough.
The [ACTION] you can do:
On weekdays, you can
-visit her house
-rest
-work (for 3000 yens)
-use items
on weekends, you go on dates instead of visiting and work is 4500 yens
When you visit, the little sister can be here. No sex if that's the case... but!
[little sister route]
You can have your way with her. Offer candy/books (the second one)/game console to her until she likes you enough to let you enter when the big sis isn't there.
Then offer her the adult book and don't have sex with the big sis. Congrats, you have a loli as a side-fuck.
Get her the swimsuit too, and you'll be able to fuck her every time big sis isn't home.
[big sis route]
When you have sex with the big sis in her house, you'll need to match her pace so you don't come too quick. Use the speed button to adjust. The blue potion will let you have a second lifebar.
This should get the third and fifth stat to raise. Each time you'll raise the fifth stat you'll get a selfie from her at night.
This will unlock sex scenes on dates (don't remember the order, sorry) , so try all the dates.
This will also unlock new positions at home.
Don't worry about time, you have no limit.
And that's it. Keep her happy on weekday, find the good date fucks on weekend.
[items]
-dildo: use it at home when her ecchi level is high enough
-rotor: used in the family restaurant date
-yellow potion: raises your health
-adult book: see little sister route
-candy: makes any sister happier
-red potion: no idea (saves you when in a pinch? I think it can be used on the family restaurant date, not sure)
-blue potion: double lifebar at home
-flowers: do you need to be forgiven?
-manga book: both sister loves it
-game console: little sister route
-charm: dunno really
-swimsuit: little sister route
That's all. Hope it helps people. I won't post savefiles because that's not fun :p
PS: the ferris wheel fuck seems to be bugged, I get a black screen)