The artwork in the earlier volumes aren't really that great, since the drawings of the characters look a bit odd (IMO). For one thing Hiwatari-sensei drew faces really roundish, with long eyes.. but all can be forgiven because the story is really wonderful, with some humor, romance, tragedy, action, etc! ^_^ And as time progresses in the later volumes, her artwork gets better and better. The eyes have shrunk a bit, and the faces are not as round, and they look almost like the OAVs!

In all, there are 21 manga toubankon. You'll be able to find the manga in Japanese and Chinese.