A mercenary teams up with a prince to rescue a princess who was kidnapped by her father who is an evil emperor.

I'm done.

- Two childhood friends, including a mercenary and a prince falls in love with each other in space until they decide to stop an evil emperor from having the town being invaded by aliens

• a mercenary and a prince.. who is your protagonist?
• 'falling in love' should not be confused as the inciting incident.
  It doesn't bring the story into action. Think of a specific event which makes her go against the emperor
  OR think what's at stake. She's in outer space, what does she have to lose with this invasion?

I revised it.