Sum up:
Like Naruto games before it, Clash of the Ninja Revolution 2 is a straight out fighting game, where you take your pick from dozens of this anime's characters, and brawl it out in side-scrolling arenas. The game adds a few new characters, stages, story, and biggest of all, "Mission Mode," which will include over 300 missions with a variety of objectives.

Recommended age:
The ESRB rated this game for "T" for Teen, listing "Cartoon Violence" and "Mild Suggestive Themes." The "Mild Cartoon Violence" obviously consists of hitting, kicking and flinging opponents in the air, while charging up your ninjitsu (basically ninja magic), and letting it fly into enemy characters.

The "Mild Suggestive Themes" probably refers to one of the main male characters who's nicknamed "Purvy (pervert) Sage," as he likes to write romance novels, and peek into the women's bathhouses, etc. Although this isn't quite as mild as Super Smash Bros. Brawl content-wise (which I gave a 7+), it's still one of the most mild fighting games you can get, with no language, blood, near naked women, or breast physics. So, I'd recommend this game for ages 10+--and if you're okay with your 7+ year-olds playing fighting games, I don't see a problem with them competing with an older sibling, etc.