It's listed on Amazon in the shoujo category but here it says shounen:

http://amzn.to/hrXRcy 😕

I was pretty confused since I though it was seinen before XD

It's shounen, it's serialized in Gangan online.

This week's favorites:

• Golden Kamui

ççççççç[Ô.Ô] tsutopodus© will eat your manga and steal your cats!

Here at BU, demographic is determined by the magazine in which the story was originally serialized. Amazon.com probably has a different method of classifying manga - hence the confusion. I've read the first few of chapters, and so far I think it feels like a shounen - albeit a fairly non-mainstream one.