So, since the game doesn't have a tutorial for its actual gameplay (presumably because it's the same as Jitaku Keibiin 1) and the MTLish doesn't help, here's a quick and dirty rundown of how it works:
You're a piece of shit who wants to blackmail (and/or drug) the beauties living in the house in order to fuck them. To do that, you use your """"status"""" as "home guard" (hikikomori) to strut around everywhere you please in the house, placing videocameras, regular cameras, and audio surveillance devices wherever there's a chance of someone getting naked to get dirt on them (and also fap material). Each type of surveillance device has a different duration they can be active for, so you need to be careful of the when you set them where, as well as which kind of device you're setting (obviously putting an audio surveillance bug in the changing room won't let you film the naked bodies in it). As you accumulate fap material you generate "threat" (the actual word used is closer to 'intimidation', i.e. how much what you have will intimidate the person you're blackmailing). When you judge you have enough you can put out an 'indictment letter' (very Detective Konan) in the room of the person you want to blackmail and after that you meet them in their room at night to threaten them and make them do whaatever you want them to do. More blackmail material= more scenes unlocked and eventually endings. You can also use the various drugs you buy from your computer to either sleep rape them or unlock peeing/masturbation scenes (assuming you have y our cameras set in the right place and the right time, of course!) by drugging the food in the kitchen around 18:00-18:30. Trick is, since there's usually someone with the food atthe time (either the maid Shieri, your 'aunt' Shiho, or both) you need to set their alarm clocks to go off at that time (in their rooms) to move them away from the kitchen so you can get access to the food.
There's also a typically convoluted story line behind this whole mess that you might accidentally stumble into if you keep bugs in the library and idk where else but it doesn't seem to unlock any more porn so it's not that important.
EDIT: Since the controls are confusing some people, you can go anywhere by clicking on the map at the top right and then clicking the room you want to go. Switch floors by clicking on the stairs.