This is a librarian review. I try to leave notes on books I’m considering for a middle school library for others in the school library profession because manga is hardly ever professionally reviewed for us to properly vet before buying. I mainly just look for troublesome issues for younger ages, such as sexual content, language, or extreme violence.
The book is rated for teens 13+. It's technically not manga, but manga inspired. (The author is Italian, not Japanese.)
Language:
The language in question consisted of various uses of hell, damn, dragon shit, g'damn, piss off, screw you, and dumbass. It happens regularly throughout the book. Volume 2 has more and even a cut-off F-bomb.
Sexual Content:
So far there is very little, which is very refreshing. There's no innuendo or inappropriate jokes between major characters, and I haven't even seen any revealing clothing. The only thing that happens is in the first few pages when, as the girl character, Ayumi, is walking home, two men cat-call her, saying "Hey, nice private school uniform; Wanna take private lessons with us?" This happens in a small montage as she considers the frustrating things in her life. More on that below.
Alcohol & Substance Abuse:
Ayumi's mother is shown in a few panels to be an alcoholic. Ayumi walks into the house to see her mother over the couch looking wasted with either liquor or wine bottles in hand. The dialogue is short between them ("Mom, you should go to bed... fine, do what you want") and the scene doesn't get into much beyond showing you what's going on with her home life that is stressing her, which is a neglectful mother, a home filled with trash, and an absent father.
In the second volume, two characters smoke cigarettes together.
Violence:
Nothing that substantial. No blood or gore. The fighting revolves around controlling elements, similar to 'Avatar: the Last Airbender' in that characters called 'Saigami' can essentially bend. Elements so far have been fire, water, earth, and air. There are also magical monsters someone mysterious sent after them while they were traveling.
Overall, I have not enjoyed this series due to the prolific use of heavier language, and the cigarettes really put me off in the second volume. We have enough issues with kids vaping in school restrooms as it is without using cigarettes to make characters look edgy and supposedly cool. The magic system is something we've already seen (Avatar: tLA) and the world building isn't interesting or fleshed out enough to make up for it in my opinion. The only genuinely good qualities at the moment seem to be the lack of sexualizing the female character and a focus on characters helping each other.