Well as a side story covering the movie this was likely a promotion on the movie. This preview was more of a reminiscent past of Yuuta, being the "dark flame master". Only Yuuta and her sister Kuzuha were only featured here so there's not much of a develepment but rather just a skit. This skit goes on with the past of Yuuta being the "dark flame master" and having a little character development for the characters that were present, specifically her mom, her sister Kuzuha and Kuzuha's friend whom always thinks that Yuuta is "cool". Though Rikka was not here, she was on the ending's screen preview, dancing, whichwas foxy and sexy.