The Kappa, one of many mythical creatures classified as "Yokai", is often translated into English as "water sprite", though that does not convey much of the character of these creatures. Stories of Kappa can be found all over Japan, but some areas have a stronger connection to them. The design above is from Tsuyama in Okayama, where the creature is known as Gongo. A Gongo festival is held every year.
South of Tsuyama, though connected by the same river system, is the town of Kumenan. The toen mascot is "Kappy". There were several different designs incorporating Kappa, but I passed through in the dark so the only photo that turned out well was the one above.
Tanushimaru along the Chikugo River in Fukuoka claims to be the original source of all Japanese Kappa. There are many Kappa shrines in the area and statues of Kappa are everywhere. The railway station is also shaped like a kappa.
The photo below is from further south in Kyushu, Satsumasendai in Kagoshima.
The best manhole design of Kappa though is the one from my town, Sakurae, where it is known as "Enko". It can be found here.