<p>The kanji for shonen literally means "few years" but it's more accurately translated as "boy" or "adolescent boy." The target demographic is teen and pre-teen boys, though the average age of its readers has steadily increased and is now something like 16 or 17. It also depends on the magazine, some shonen magazines target older demographics and are basically seinen magazines in everything but name, and some seinen magazine run series that would be perfectly fine in a shonen magazine.
</p><p>In terms of what is considered graphic, it depends on the medium, since there are different ratings boards for each. Restrictions for manga are fairly lenient, as they're black and white still images. It's not that it's considered "tame," just that it's not considered harmful.
</p><p>Television censorship depends entirely on timeslot and the network, much like in the US. Most graphic anime series are aired only after midnight, and almost all anime is censored to some degree when televised, with DVDs being uncut (the same is true for <i>Naruto</i>).
</p><p>Video games in Japan are actually very strictly censored because players are actually in control of the actions, and a lot of M-rated (17+) Western games are heavily censored when released in Japan to avoid a Cero-Z (adults only) rating.
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But, yes, <i>Naruto</i> was aimed primarily at a pre-teen/teen audience, many of whom obviously grew up over the course of the series. Kishimoto also definitely toned down the violence after the chunin exams, around when the anime started airing. It is a pretty tame manga, regardless, especially when compared to a lot of <i>seinen</i> series that target young adults.
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