I am so sorry for you. I really, really hate spiders!
Well, after looking at many disgusting pictures of these creatures on Wikipedia, all I can really say is to go around your house and get rid of any
webs, including in the trees. Not much help there.
I'm not sure where you get them, but they do have these little "boxes" I guess you could call them, that are supposed to give off sound waves that
are silent to humans and pets but repell things like bugs and mice. I have one myself, but I got it to try and ward off bats (to no avail). Maybe they
do work, I have a few stray bugs that wander in here and there, but I can't garantee it.
Since you mentioned the houses are poorly built in Japan in your area, maybe you could go around your house with a caulk gun and try and seal up any
holes or cracks they might be coming in from. It probably won't help a whole lot, but it's worth a shot.
My last suggestion is to get some really, really potent bug repellant spray. You know, the really toxic stuff you can't spray around children or
pets- and just spray a ton around your house a few times a week.
Wait-I guess you could call an exterminator...

Really, though, spiders aren't all THAT bad. They're probably keeping even more bugs from coming into your house.
Hope that helps!