I cant buy it over steam, because steam laws dont allow it in my country. So i cant use steam keys. I know that there are underaged idols, but i played the demo and u cant flirt with them, at least not in the demo.  Its a bit silly, that murder Games etc. are legal, but games with flirting with adult women are illegal ^^" 

I am new to itch.io, so when i buy games here, i can download them on my pc? And the steam key just comes extra?

>I am new to itch.io, so when i buy games here, i can download them on my pc? And the steam key just comes extra?

Yes, but the Steam key that you'll get should actually work for you too, even if you're in one of the countries where the game isn't available