The purportedly true story of a 23-year-old otaku (Japanese geek) who intervened when a drunk man was harassing a woman on a train. The otaku ultimately started dating with her and chronicled his event and his dates with the woman (who became known as "Hermès") on the Japanese mega-BBS 2channel.
Acting
Takayuki Yamada's full-body awkwardness is genuinely painful
Writing
BBS comments as Greek chorus: surprisingly effective

Director
Shosuke Murakami
Trivia, insights & behind the scenes
This spawned an entire 'Densha Otoko' media empire—drama, manga, even a stage play—because Japan couldn't get enough of this allegedly true story. The original 2chan threads are still archived online.
The real 'Hermès' was never publicly identified; some skeptics believe the entire story was collaborative fiction written by multiple 2chan users.