Okay, this was (is) one of my favorite mangas. Then I saw it on YouTube.com and it changed my freaking life!
Title: Flame of Recca
Age group most suited for it: Definitely starting with younger teens because of the violence in later episodes.
Genre: Action with a bit of romance
Summary: M'kay, I got this from Wikipedia:
Flame of Recca is about a highschool student named Recca Hanabishi, who aspires to be a ninja and is obsessed with anything ninja-related. After meeting a girl named Yanagi Sakoshita, whom he acknowledged to be his princess , and a mysterious woman named Shadow (Kage Hōshi), who apparently attacked him for no reason at all, he finds that he not only comes from a long-dead ninja clan of 400-years past, he also can control his personal Flame. Recca and his friends (Domon Ishijima, Fuko Kirisawa, Tokiya Mikagami, Kaoru Koganei) must grow stronger in order to protect Yanagi from being taken by Kurei and his adoptive father, the evil Kouran Mori, who wants eternal life, and believes that Yanagi's mysterious healing power is the key to it.
1-10: 13
Picture (optional):It's Tokiya, my favorite character.