The game is in full English, and has been updated multiple times.
Awesome graphic and voices for a simple "choose the scene" game where this young woman (who is over 18) does things with a guy she calls her "brother" but they aren't actually related because incest is wrong, Mmmmkay.
A very simple game at its core, Kare Kano's gameplay consists of a very limited traditional VN dating sim style, where the protagonist chooses actions for the day that affect his statistics.
The actual sex simulation gameplay is pretty standard. You can browse the online repository of other players' heroines and date, then ultimately steal them. The game's dialogue is very mediocre and unimportant. The game also comes with one of the best character creators on the market, also featuring online options for finding more outfits and features.
No eroge novels (aka 'erotic visual novels') in this list: there are so many of them that we have made a page just for them.