I wasn't expecting so much from this manga... but... what a great way to start off a series!
The manga kicks off quick, fast and smooth - with no lingering around small, insignificant events. Aside from the quick-paced action that could be expected of a shonen manga like this, I think Ryo Saenagi does an excellent job of creating characters that are easy to become attached to - including Nanaki's sheer cockiness and stupidity, which always finds some way of making readers laugh. This manga was hilarious, no questions asked.
Saenagi also begins to explore some more emotional aspects that may be affecting (or have yet to affect) characters, which provides some depth that will probably be able to carry the series farther than had it gone on psychic abilities and secret government organizations alone.
As critical as I can usually be, I could find little wrong with this. Perhaps only the fact that the idea of ghosts and/or psychics and/or secret government organizations has been taken a million times already, (though, suprisingly, this doesn't seem to detract too much from quality) and the fact that the end coul have left off on a little more of a cliffhanger to drive readers on to the next book.
It's too early for me to judge much else... but from what I've gotten out of volume one, I'd highly reccomend this to any manga fan!
Note: Though Ryo Saenagi may be the author of other yaoi manga (I just recently found out), this one doesn't seem to lean towards that genre... as far as Volume 1 goes, that is.