So what's the story with the mayor's hat? Tajimi's mascot is the "unagappa", a combination of the two words "unagi" (eel) and "kappa", a mythological creature believed to live in the rivers of Japan. You can see a depiction of the "real" Kappa here, as imagined by an 18th century artist. Eel - as cooked according to the local tradition in Tajimi - is really something else! So, the famous creator of the "Anpanman" character, came up with the idea of combining the Kappa and an eel into the Unagappa, which inspired the design of the mayor's hat, souvenirs, T-shirts, and many other items.
By Toriyama Sekien (Japanese, *1712, †1788) [Public domain], via Wikimedia Commons