Kudos to the writer for spelling out seven instead of using the numeral.
There needs to be a comma after princess (dependent clause preceding main clause).
It makes more sense to say ride instead of gallop; the horse gallops, not the person/people on it.
When he arrived to rescue the princess, he did not expect to find seven other girls hidden in the tower with her. Now how were they supposed to ride romantically into the sunset on his horse?