The entire series is about a PkP game (player kills player) so of course there are LOTS of battles. However they are mild game-based with no wounds, visible damage, or blood. Plenty of violence but no gore.

In the English subtitles there is ONE singular F-bomb.

In 40 episodes there are only 2 or 3 scenes of drinking alcohol. In fact, alcohol is banned for all gamers and the show presents it as damaging to skills and mental prowess.

Unless one considers mild PvP gaming to be intense and scary, there is nothing in this that would be considered genuinely frightening. Even the "bad guys" aren't so bad. The gaming scenes can be a little intense as one wonders who is going to win or lose, but nothing bothersome.