I'm looking for something along the lines of:

Welcome to the NHK!
Genshiken
5 centimeters per second

Can't really explain what I really liked in those series, but all of them gave me a bittersweet feeling. I'm looking for an anime that deals with more of an adult theme (not hentai), doesn't rely on fan service and harem jokes to fill up an episode. Yeah I know my request is kinda hard, but I hope someone might be able to help.