"A miraculous creature known as the Misago lives and fishes in Koajiro's cove...She doesn't like adults, but sometimes, she comes out to play with children. But because of her scary fangs, they always run away."
--Manga Project translation--
The Misago appears in a manga by Ashinano Hitoshi called Yokohama Kaidashi Kikou. There is currently not an official English translation, however there are a couple of fan translations available online: There is one on this site and another available from Manga Project.
What is the Misago exactly? Is she a human? A robot? Something else completely? At this point, that remains a mystery. However, it is the mystery that makes her intriguing. Well, that and her cool fangs!
She only appears to children. So far, we know that she was spotted by Ayase, Takahiro, Makki, and Alpha's mysterious owner.
If you are a fan of the Misago, read the rules and join the fanlisting. A fanlisting is, just as the name suggests, a list of fans of a particular subject.