This is a movie about Miyavi, which means: if you like Miyavi running around looking good (and just being miyavi) then this is the movie for you. The story is about how the super-famous Miyavi travels back in time to meet himself as a kid. If you know why Miyavi stopped playing soccer then you'll know the most of the movie.
So, the movie is about Miyavi playing soccer, guitar, meeting friends... If you like myv you have to watch it! If you don't, then I wouldn't recommend it.