Tenkai Rogue

Lost Key is the fifteenth episode of Tenkai Knights. It first aired on November 30, 2013 on Cartoon Network in the United States.

Plot
On Quarton, a new villain, Venetta, starts attacking the Corekai. While on Earth, Gen continues his search for the Black Dragon Key. Beni grows bored with this and schemes to learn more about Guren. While investigating Guren, Beni can't understand what makes him special. She then decides to meet him in person.

The next day, after school is done, Guren heads home when he saves a girl from falling on her face due to a busted shoe. The girl is actually Beni, who setup the situation to make Guren think he'd rescued her. Once Guren notices her shoe, he offers her a pair of old sandals to wear in the meantime. Beni then drags Guren to the mall to look for a more permanent replacement. All this is happening while the other boys wait for Guren to arrive at the shop.

While Beni shops, Guren notes how strange she is, but finds her to be a nice person. Later, Guren notes that she should get her old shoes fixed despite her claims that they are old and useless. Beni leaves but not before asking to meet Guren again, he agrees, then realizes he's late and the other boys are probably expecting him.

When Guren arrives, Toxsa and Ceylan scold him before they go to Quarton. When they arrive, they learn from Beag that a scouting party was lost, and that they were defeated by a single enemy. Distracted by a smokescreen, the Knights and Beag retreat.

Back on Earth, Beni notes that she doesn't see Guren as dangerous as Gen does and claims she could defeat him easily. The next day, Beni meets Guren again and is surprised to learn he had her old shoes repaired for her. Guren then rushes off to meet the others at the shop. Once at the shop, the boys come up with a strategy to defeat their new adversary.

Once they arrive on Quarton, they're ambushed by Venetta again. This time, they transform into Titan Mode to face her, but she proves too fast and too strong for them despite their transformation. When she has Bravenwolf restrained with her web, she tells him her name and prepares to finish him off. Once the smoke clears from her attack, Bravenwolf reveals that he transformed back to his base form to avoid her attack. When her Tenkai Energy was drained and the other three Knights were ready to fight her, Venetta retreats.

Trivia

 * Venetta makes her first appearance but does not transform into Titan mode.