Shōnen, seinen, shōjo, josei: what they mean

In Japan, manga usually comes out first in weekly or monthly magazines, and each magazine targets an audience. That is where demographics come from: they indicate the reader the magazine had in mind, not the type of story.

• Shōnen: aimed at young boys. Magazines like Weekly Shōnen Jump have published many famous action series.
• Shōjo: aimed at young girls, often focused on relationships and emotions.
• Seinen: aimed at adult men, with more mature themes and pacing.
• Josei: aimed at adult women, often about work, routine and relationships.

A label is not a rule

An action story can be seinen, and a romance can be shōnen. And anyone can read any demographic. The label helps predict the tone, but it doesn't limit the audience.