WARNING: The following contains spoilers for Season 5, Episode 4 "Make It Happen, Shinso!" of My Hero Academia, now streaming on Crunchyroll, Funimation and Hulu.
The students of U.A. have faced real villains multiple times, such as when the League of Villains stormed USJ (Unforeseen Simulation Joint) or when Tenya Iida and his classmates faced Stain the Hero Killer. Right now, Classes 1-A and 1-B are training under the watchful eyes of Shota Aizawa and Vlad King, and the students are eager to show off what they've learned -- especially Tsuyu Asui.
Tsuyu was there when the League of Villains attacked USJ and has proven herself a smart, cool-headed teammate when the fighting starts. Her frog-like Quirk has proven useful more than once, but Tsuyu's been holding back. In Season 5, Episode 4, she unveils her newest trick.
Class 1-A has a bonus member for the first practice battle: Hitoshi Shinso, who has since been taken under Shota Aizawa's wing as an apprentice. But not even Shinso's remarkable Brainwashing Quirk can defeat Class 1-B's team alone, especially when Jurota Shishida uses his sharp nose to keep track of Tsuyu's team at all times. Combined with Ibara Shiozaki's vines, it's nearly impossible for Class 1-A to ambush and capture their opponents, so Tsuyu has to get resourceful.
Tsuyu's newest trick didn't come out of the blue. Back in Season 1 when she, Izuku and Minoru Mineta were cornered by aquatic villains, Tsuyu explained all of her Frog Quirk's attributes, from her strong tongue to her superior swimming ability. She also mentioned her mildly toxic slime and the ability to wash her stomach externally, but she's kept those powers restrained -- until now.
Jurota's strong nose can detect where each of his enemies is and even tell them apart, and with Koji Koda the animal master and Eijiro Kirishima captured, Tsuyu must pick up the slack. She unveils her toxic slime ability to create some scent-based camouflage. Off-screen, Tsuyu slathers both Shinso and Denki Kaminari in her slimy mucus, meaning both boys now have Tsuyu's strong and distinct scent. With that prep in place, the three of them charge toward Class 1-B's position, confident they can fool Jurota.
And it works. Jurota is bewildered to smell three Tsuyu Asuis approaching, and no one, not even the spectators, saw this coming. Jurota and his allies can't identify Denki until he appears in person, leaving Class 1-B only a split second to face him. The real Tsuyu maneuvers in the battlefield's periphery while Denki takes up everyone's attention, and she soon captures Hiryu Rin and Ibara Shiozaki with her tongue. Jurota then corners Hitoshi, only to get hit on the head, and Tsuyu strikes him with Hiryu from behind.
Shinso's and Tsuyu's Quirks both throw Class 1-B's team into total disarray, leading to Class 1-A's first victory. Getting covered in slime has never felt so good.