While Yuma is down, his allies step up. Specifically, Kaito (Kite) Tenjo arrives to face the Barian Emperors, standing as the "single blue shadow" protecting his friends.
The celebration is interrupted when a group of "duelists" led by a man named Nelson Andrews (who plays the character "ESPer Robin") causes a scene. Yuma eventually faces off against a mysterious challenger while the tension for the upcoming finals builds. Yu-Gi-Oh! Zexal Second Episode 50
This episode takes place on the eve of the World Duel Carnival (WDC) finals in Heartland City. While Yuma is down, his allies step up
A massive invitation-only party is held for the 23 finalists of the WDC. Yuma Tsukumo is excited to attend, but his friends—who aren't finalists—initially feel left out until Flip finds a way to sneak everyone in. Yuma eventually faces off against a mysterious challenger
If you meant the 50th episode of the second series, the tone is much darker as the Barian Invasion reaches its peak.
Yuma, Astral, Tori, Shark, Kite, and the introduction/reappearance of various WDC finalists.