WARNING: The following contains spoilers for My Hero Academia Season 5, Episode 5, "Operation New Improv Moves," now streaming on Crunchyroll, Funimation and Hulu.
In many shonen anime, rivalries develop between major characters and even supporting characters. My Hero Academia has been no stranger to this, with Midoriya and Bakugou's rivalry being the most prominent in the series; however, there are others between characters like Kirishima and Tetsutetsu, as well as the new rivalry between Yaoyorozu and Kendo. Another rivalry has been introduced in Season 5, Episode 5, "Operation New Improv Moves," between Class 1-A's Tokoyami and Class 1-B's Kuroiro, a.k.a. Vantablack.
At the start of the episode, the classes' respective teams enter the training area, with Yaoyorozu, Tokoyami, Aoyama and Hagakure representing 1-A and Kendo, Kuroiro, Komori and Fukidashi representing 1-B. Prior to beginning, two rivalries form, with Kendo admitting to Yaoyorozu that she's been waiting for a chance to properly fight her, and Yaoyorozu accepts her challenge. Meanwhile, Vantablack tells Tokoyami they are the same, as he believes they share a destiny. Tokoyami seems to agree with him, as they both are supporters of the deep.
This isn't too surprising since their Quirks thrive off of darkness. Tokoyami's Dark Shadow grows more powerful and uncontrollable in the dark, while Vantablack can merge with anything dark; however, there is more to this Quirk, as revealed in this week's episode. After Tokoyami sends out Dark Shadow to find the 1-B team, Vantablack is able to merge with Dark Shadow, taking control of him. Vantablack has developed his Quirk so he can take control of the dark things he merges with, as long as they were able to move beforehand.
He then appears to target Tokoyami, claiming he will vanquish him. Tokoyami accepts this challenge; however, Vantablack lives up to his title as the Scheming Hero because this rivalry was a distraction. While they share similar Quirks and are rivals in this competition, Vantablack's targets are Tokoyami's teammates, even though Tokoyami initially thinks Vantablack is only after him. He intentionally planted the seeds for Tokoyami to believe this to catch him and the others off guard, successfully grabbing Aoyama.
Thankfully for team 1-A, Tokoyami also has a trick up his sleeve. After working under Hawks, he developed a new skill --Dark Fallen Angel. Using his cloak, Tokoyami protects Dark Shadow from the light while his Quirk holds onto him and makes them both levitate. This gives Tokoyami the opportunity to save Aoyama while the Sparkling Hero uses his Quirk -- Naval Laser -- to alter the shadows and force Vantablack out.
This was only plan A for Class 1-B, with Kendo instructing Komori to use her Quirk against Yaoyorozu and Hagakure in retaliation. While this rivalry was primarily a distraction, there is no doubt that Tokoyami and Vantablack are true rivals after this, especially after Kuroiro took over Dark Shadow and launched a surprise attack on Tokoyami's friends.