Comics (especially Manga) are often not pushed in front of any standardised ratings board before going on sale, and the age ratings from the publisher often seem very lax - and possibly deliberately to sell more books! Or possibly I'm just a little old and out of touch.

Anyway, when writing about a Comic I'll try to look at the level of the language, the level of violence, if there is any blood or gore, and how much skin that characters are showing. If I feel that there's a lot, or if I feel the Comic edges over some kind of boundery, then I'll class the Comic as Mature.

Whatever it was, a Mature Comic had something in it that I didn't think should be seen by little children.