Easiest recommendation is a great game that is free. Not the newest game, and it's not bursting with hentai scenes, but it does have excellent story and engaging characters. Expect a slow-burn vanilla ride in a game made by first time devs that is still better than many done by seasoned professionals.
Katawa Shoujo on FAKKU
The story on how the game came about is interesting on its own as well.
Hentai Game that Broke 4Chan