Tsuruoka's Tenjin Matsuri is held every year on May 25th.
During this occasion, hundreds of masked men, the "bakemono" (bakemono 化けもの : "disguised men") walk Tsuruoka's streets with sake bottles and cups in their hands. Their purpose? Serve sake for free to anyone who wants it. If you feel like having a cup of sake, feel free to ask them. But don't expect them to talk with you. Bakemono cannot speak. They don't want to be recognized by the sound of their voice.

Tenjin Matsuri's origins:

The Tenjin Matsuri is a festival held in many cities across Japan. It is usually organized by shrines dedicated to the Tenjin god, also known as Sugawara no Michizane's holy spirit. Sugawara no Michizane (845-903) was a skillful and brilliant poet who also served as the Minister of the Right, a highly valued position, at the court of Emperor Uda. While Emperor Uda had entire trust in Michizane, his son, to whom he left the power in 897, preferred to listen to Fujiwara no Tokihira, a rival of Michizane's. Fujiwara no Tokihira plotted to have Michizane ousted from political life. Based on Fujiwara's lies, Michizane was exiled in 901 to Kyushu, where he died in misery two years later. After his death, a succession of disasters hit the country, particularly those who had participated in Michizane's exile. Plagues, thunders, droughts, deaths... The people in Kyoto were sure it was Michizane's venging spirit unleashing its rage.

To soothe Michizane's wrath, the Japanese people raised him to the rank of a god: Tenjin 天神, the god of thunders and knowledge.
Every year, in all the Tenmangu (shrines dedicated to Tenjin), people celebrate Sugawara no Michizane's greatness.

In Tsuruoka, people celebrate by recreating their version of Michizane's exile story. According to them, the people of Kyoto who loved Michizane so much could not possibly let the poet go without giving him a goodbye festival.
But the authorities severely punished those who illegally talked to an exile, as it was forbidden by law. The people hid their faces in clothes, wore large hats and genderless clothes, so nobody recognized them. Because snitches could still identify them by their voice, the masked men did not speak a word.
They showed their love to Michizane by organizing a silent festival where sake flowed freely.