Plot/Story
IO basically starts of as a typical romantic comedy with an average guy who goes to Okinawa and meets some sisters who he happened to know before, yet he can't seem to recall any of his past with them. Yet behind what would seem like a typical romantic comedy is a story of supernatural mystery, ancient relics and scuba diving. The way in which the story is told is simply amazing because as you continue to read, you just don’t know what to expect next. There are plenty of twist and turns, in the story, but everything manages to come together in the end.

Characters
The characters are amazingly well-defined that it is easy to notice little things about the way they interact with one another. There are also quite of few of them which are somewhat mysterious and you’ll be wondering who you can trust. The only problem is that some of the things the characters tend to do can seem idiotic or annoying.

Drawing Style
The artwork is one of the best things about the manga and in the beginning you may not think that but gradually the artwork becomes flawless. There is so much detail put on every page, you begin to notice little flaws like the eye lines and how one of the girls looks like a boy, at times (Shibuki). This manga will one day also become known for the few beautiful colour pages of the best fanservice ever created.

Overall / Enjoyment
I came into this manga thinking it will be just an average manga but it surprised the heck out of me because it far surpassed my expectations. One of the best aspects of IO is the romance and it makes it all so believable, which is a nice change from all the cliched romance manga manga you can find (e.g. I’s Pure and Ichigo 100%). After a slow start the story begins to unravel itself and becomes so interesting to read. It's able to suck most people into all the mystery, forcing you to read on, to discover more.

^_^