Inspire by Ressha Sentai Toqger.
The Shadow Railroad line has return after being imprison for thousands of years & plotting their revenge against the wonder city. A family-owned business: the railroad rainbow line, their father has disappeared when he has his children prepare to fight against the shadow monsters to become: Power Rangers!
While David is still feeling depressed with his father's disappearance, he befriends with a young boy who's lonely but scared by a shadow monster who challenges anyone to a duel fight.