The bird with three legs (also called tripedal) is a mythical creature encountered in many traditional legends from Asia and North Africa. In Korea it is known as Samjokgo and is a symbol of power, while in China the three-legged bird is called Sanzuniao, is usually represented in red and is associated with the sun.
In the Japanese mythology, the three-legged bird is named Yatagarasu “eight-span crow” 「八咫烏」, is represented in black and is the symbol of divine intervention in the human world.
According to the legend, Yatagarasu was sent by Kami Amaterasu to guide Emperor Jimmu during his eastern campaign from Kumano to Yamato.
Tsukioka Yoshitoshi - Emperor Jimmu, guided by Yatagarasu, image via Wikipedia
Since Yatagarasu is so strongly connected to the Shinto religion, is no wonder that we can see it at Shinto shrines, represented on ema or on omamori:
Yatagarasu Omamori, Fukagawa Fudoson Temple
Another interesting fact, Yatagarasu is currently the symbol of the Japan Football Association (JFA), and you can even buy omamori with the JFA Yatagarasu! ;)
Yatagarasu Omamori, Fukagawa Fudoson Temple