Umitomo
Umitomo, the Japanese Holiday, started in 15 B.C. with the death of Emperor Umito. Umito, once a peasant, stole the hearts of the people at a young age by marrying Princess Kumiko at the age of 11. It has been said that upon taking The Throne at 15 his first official act was to re-instate the rule of divinity in relation to the royal family, although this is very contested.
Not much is known AbOUT his rule, as it only lasted for 3 months. What is known is that he is directly responsible for Umitomo - the Japanese day of giftgiving and respect. History tells a different story about Umitomo, but popular history of Japan still attributes the day to the mostly forgotten emperor. Kumiko, who is perhaps better known as Empress Kia, killed her husband after 3 months, although this has never been truly proven.
Umitomo is little celebrated today, and has mostly become a forgotten footnote in Japan's honored history.
Sources
"Glencoe World History: Teachers EDition", Glecoe Press, New York 2004