This is Part 5 of stories about Lord Taira no Masakado.
Near Palaceside Building, places connected to Masakado still remain. One is Tsukudo Shrine, one stop northwest on the Tozai Line from Takebashi Station at Kudanshita. It sits in a gap between buildings behind Kitano Maru Square (the former Japan Bond Credit Bank headquarters) in front of the station, reborn as a concrete-walled shrine hall and building after a major renovation in 1994.
According to the shrine's website (which does not appear to have been updated recently), in 940, after Masakado was slain and his head was paraded to Kyoto, it was placed in a head bucket, secretly taken away, and enshrined at a Kannon hall near present-day Otemachi, where it was called "Tsukudo Myojin"—said to be the origin of the shrine.
Wait—didn't the head fly from Kyoto to Masakado's mound? Well, it's legend.
After Edo Castle was built, a shrine hall was placed northwest of the castle in 1478; it was later called Tian'an Myojin and Edo Myojin, and counted among the Three Great Shrines of Edo along with Hie (Hie Shrine) and Kanda (Kanda Myojin). The site moved through Tian'an, Ushigome, Tsukudo Hachiman-cho, Fujimi, and others before relocating to present-day Kudankita in 1954.
Relations with the Tokugawa shogunate seem to have been good, but in the Meiji era, in 1874 (Meiji 7), Amaterasu Omikami's grandson Ame-no-Hikoho-ninigi-no-Mikoto was enshrined as the "chief deity," and Masakado was "demoted" to a secondary god worshipped alongside. The website explains that "a trend emerged in some quarters to regard Masakado as a 'rebel' who defied the emperor," and that "for convenience, a deity closely linked to the emperor was elevated as the 'chief deity'..." It says the shrine did not publicly declare itself a shrine honoring Masakado again until 1990.
Masakado's head bucket was kept as a shrine treasure; it was feared that "those who look upon it will go blind," but it was lost in an air raid in Showa 20. A photograph taken in the Taisho era appears on the website.