PG-13 - Parents Strongly Cautioned - Some material may be inappropriate for children under 13. Films given this rating may contain sexual content, brief or partial nudity, some strong language and innuendo, humor, mature themes,
political themes, terror and/or intense action violence. However, bloodshed is rarely present.
R - Restricted - Under 17 requires accompanying parent or legal guardian. The person is required to stay with the child under 17 through the entire movie, even if the parent gives the child/teenager permission to see the film alone. These films may contain strong profanity, graphic sexuality, nudity, strong violence, horror, gore, and strong drug use. A movie rated R for profanity often has more severe or frequent language than the PG-13 rating would permit. An R-rated movie may have more blood, gore, drug use, nudity, or graphic sexuality than a PG-13 movie would admit.
NC-17 - No One 17 And Under Admitted - These films contain excessive graphic violence, intense or explicit sex, depraved, abhorrent behavior, explicit drug abuse, strong language, explicit nudity, or any other elements which, at present, most parents would consider too strong and therefore off-limits for viewing by their children and teens.
So NightAngel would go under NC17, lol. Though...95% of the series is PG13