Coo is the Kappa the whole story revolves around. He is found by Koichi Uehara, after he had survived over 200 years as a fossil. He then lives with Uehara family. 

Kouichi Uehara is a fourth grade student living in the suburb of Tokyo. One day, he picks up a large stone which turns out to be a fossil of a baby "Kappa" sleeping underground for the past 300 years, and names it "Coo". Koichi and Coo become good friends and starts living with his family. However, Coo could not adjust to the life style in Tokyo and starts to miss his family. On a hot summer day, Koichi and Coo decide to go on an adventurous road trip to find his peers. <br><br>
(Source: AniDB) 

[Wiki (jp)](http://ja.wikipedia.org/wiki/冨澤風斗)

Tanya is the station voice of "YOU FM" ("Young Fresh Music", Hessian radio station: http://www.you-fm.de/)