ensha Otoko (translated as Train Man) is a Japanese movie based on 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.

Overview from themoviedb.org