First I thought this was a shoujo. The plot is very girly to me. And it turned out it is a shounen... although it makes kind of sense, if you look at the art.
It is not a bad manga, it is funny, but very silly... and awkward. I seriously was not compelling to read it, but the woman that sells me manga recommended it to me several times, and one day, when I did not find anything else to buy -and I knew I could not leave with empty hands- I bought it.
How awkward is to have a girl -a girl who knows you, who is actually a normal girl with family and friends- living in your right hand? Seiji has problems to even go the bathroom, not to mention to write in class, have exercises, fight with other guys, etc.
I admit I enjoyed it; I laughed several parts but I will not continue reading it.