AKA: Noein - Mou Hitori no Kimi e
12-year-old Haruka and her friends are living fairly ordinary lives, until one night when the crew decides to go ghost-hunting. There, Haruka meets a mysterious man in a black cloak named Karasu (Crow). He claims to be one of Haruka's friends (Yuu) from 15 years in the future. More strange events begin to happen around Haruka, and she discovers that she is the "Dragon's Torque," the key to stopping the eventual invasion/destroyal of her world.
Noein's plot is much more complex than that, however, and the character development is - in a word - magnificent. Even the minor characters receive attention, and the various relationships between the members of the cast are interesting and fleshed-out. By the end of this series you will probably have at least one character you feel really attached to (for me it was Tobi, who is awesome).
One of the first things you notice about Noein is its unique style of animation. This may throw off some people who are expecting this series to look like your typical anime, but in my opinion, the art/animation is some of the best I've ever seen. Character movements are smooth, the backgrounds are detailed, the action scenes are amazing, and the character designs are really nice. Some people feel differently about the visuals, though, and I guess it just boils down to a matter of personal taste.
The soundtrack is appropriate for the series and helps along the emotional scenes quite nicely, but it never really stood out to me (probably because I was trying to piece together the plot most of the time XD). The opening and ending themes are both nice, especially the opening, which has some really pretty lyrics.
With its wonderful characters, original animation, and overall epic atmosphere, Noein is a series I highly recommend. It has action, drama, and a little bit of comedy and romance, so it can easily be watched by most anime fans. It's a shame this series isn't more well known.