Train Man by Nakano Hitori

Train Man is a love story set in Japan and told through threads on the chat forum 2-Channel. One day, a geek is riding the train when he notices a drunken old man harassing some women. In a rare display of courage, he steps in and defends the women. Not to say that he performs some heroic feat; he just tells the guy off rather than pretending that nothing is happening (which would be the more typical response). The old man tries to pick a fight, and at that point another passenger steps in to help. At the next station, the pervert is arrested and the women on the train thank him for defending them. One of them happens to be young and rather attractive; she was the person sitting next to him before the commotion started. The geek relates this story to his friends on 2-Channel, and is dubbed Train Man from here on out.