Woshite World has posted three articles about the Hinamatsuri Peach Festival, also known as Girls Day or Dolls Day on March 3.
“It is said that Hinamatsuri originated in the Heian period as a form of play with dolls. In modern times it is a Girls Day festival held on the third day of March. One of the main elements is a display of dolls of Emperor and Empress (Tennnou and Kougou) and their court in Heian period dress. This is the true story behind Hinamatsuri and it reveals why it is also the peach blossom festival. This is the charming tale of childhood friends who became the fourth Amakami. The deep significance to their wedding is that it was the first time that the Amakami were recognized as a couple, and this led to societal changeover to a family-based system.”
The origin of this festival is described in Hotsuma Tsutae, Verse 265ff. It is the love story of the fourth Amakami, Uhitini and Suhitini. You can read the first part of the three-part post here: