Even though this OVA is good, it would've been better if there was more plot to the story. The characters were good, but they don't tell how Kai and Shou got separated and who the Black Winged dude with the eye-patch was at the end of the second OVA. They don't even continue with what happened with Naoto and if Nagi really was dead.
I wish it would be a full series with a better plot and better storyline. I like the characters, but it would be better with a better plot for most o them.