Japanese movie from 2005, starring Eita, Ueno Juri, etc.

I was supposed to be going to the mountains today, but instead we're going tomorrow morning and thus, I watched a movie online instead

Either way, I highly recommend this movie due to its originality, creativity and of course fun..niness...(not a word), and you can find it on video sites such as tudou or crunchyroll, I think...

Image from English wikipedia