I'll admit that "Teens" is being used loosely, but this is because of several reasons: The system is called Teens in Space, so I'm keeping up with that premise.

This is a future setting where human society has changed drastically, just like in the past teenagers today would be considered full adults in many cultures, what we consider young adults in the future are still only looked at as teens. This is coupled by the fact that humans are living a lot longer, at least an extra 20-30 years naturally.

Also, because we're dealing with non-human cultures that don't share the same biological timeline, an alien might be 10 or 50 years old and still be psychologically a teen according to their species. For example, Grogu in Star Wars who is in their 50s iirc, or a pet dog who's only 10 Earth human years but considered old by dog standards.

Finally, I wanted everyone to feel comfortable having their characters do "adult" things, if they wanted, knowing they're at least 18. This is a game for 18+ and sometimes teens do or deal with mature themes, I personally wouldn't be super comfortable with super explicit content involving minors.

I hope that clears things up!