Hi. Just wanted to add some help for the people who have a hard time unlocking the threesome / foursome skills.
Every girl has vigilance. If you talk to them, you should see how high it is. Uncle has vigilance too.
Get both sisters to level 4 or higher, which means to 80 affection or more. Unlock at least some lewd h skills.
Buy lots of coffee drinks or other drinks that raise stamina. About 5 or more.
Have full stamina. Save right in the morning. Change the time period and check the map.
The sisters should be in their own rooms - or - as close as possible to each other while in different rooms in the house. Otherwise reload and change time period again. Yui being in the kitchen and Rio being in front of the TV should also work.
When you finally get them close in the house, save on a new save slot. Talk to Yui and have sex. The silent skill has to be turned OFF. Choose a lewd skill. Press the left mouse button and get the sex intensity bar as high as possible, this makes the sex noisiest. Lose 30 or 50 stamina and then cum. Do it a few times by drinking stamina drinks. save. go talk to Miyuki and Rio. Check their vigilance. Get it high enough, reload if necessary.
If Miyuki's and uncle's vigilance are higher than Rio's vigilance, that's not good, cause they are going to discover you before Rio and it's game over.
Before pushing Rio's vigilance to 100, reduce mother's and uncle's vigilance.
- giving most cheap gifts reduces vigilance by 5, get the 2 gifts per day skill, give uncle and Miyuki 2 fish baits every day over 2 or 3 days
- sleeping with Miyuki, doing her homework or spending time with her - each should reduce her vigilance
- spend time with uncle - reduces his vigilance by 20
When uncle's and aunt's vigilance are finally below Rio's, go back to Yui and have lewd noisy sex with her over and over.
Rio will finally catch you in the act.
Foursome is much easier. When you get the threesome skill, you can press it and invoke it anytime. This brings the scene up even if the sisters are sleeping, bathing or on the toilet (if I'm not wrong).
Lower uncle's vigilance below Miyuki's and have a noisy lewd threesome until Miyuki catches you.
Keeping in mind
- when banging Yui, it doesn't matter if Rio or Miyuki are sleeping, their vigilance will go up regardless.
- uncle's vigilance shouldn't be going up if he isn't at home - when he is at work.
Generally
It helps a lot to go to the mountain and run up the mountain every night when your AP is full. Get higher stamina and bath daily to restore it.
It helps a lot to catch a lot of bugs throughout the month, and then eventually sell them to the biologist girl at the bottom of the mountain. Get a lot of yen and buy lots of stamina restoring drinks.