Deku's Blackwhip Ability From My Hero Academia Explained

In the "My Hero Academia" world, where 80% of the population has special abilities known as Quirks, a hopeful student would have to have quite the unique Quirk to reach his superhero dreams. Luckily for Izuku Mydoria, aka Deku, his Quirk is probably the anime stuff made of a Shonen Jump protagonist's dreams. Despite actually being born without a Quirk, Deku inherits a superpower known as One For All from the superhero All Might. One For All is a powerful Quirk that comes with a disturbing truth thanks to its origin. The Quirk only exists in large part because of the series' most dangerous villain, All For One. But in addition to this grisly revelation, One For All also has numerous past users who Deku begins learning about and even talking to in his mind.

After subconsciously coming into contact with the previous owners of the One For All Quirk throughout the manga and anime, Deku opens the powered floodgates to several new impressive abilities, which is quite the leap for someone who started Quirkless. One of the powers Deku gains is known as Blackwhip, which proves to be both a formidable ability and at times too uncontrollable for the young hero.

In "My Hero Academia" manga Chapter 210 (via Viz Media), dark tendrils made of energy begin emerging from Deku's body during the Joint Training Battle. The power proves too uncontrollable for Deku, who goes unconscious soon after it debuts. It's not until Chapter 212 that Deku gets more of an explanation about the new power in his subconscious from a previous One For All inheritor named Daigoro Banjo. The former hero explains that when Deku has a thought of wanting to capture somebody, his Quirk Blackwhip activates as it's the perfect ability to catch someone.

Daigoro is correct, but as we see throughout the series, Deku develops some innovative uses for the ability. Throughout "My Hero Academia," Deku uses the Blackwhip ability to attack someone by shooting a tendril out of his hand, and he also uses the Quirk to quickly launch himself through the air, much like the web-slinging Spider-Man. With both of his arms broken in Chapter 293, he even imitates his teammate Tsuyu Asui — who has a frog-like ability to extend her tongue over 20 meters — and shoots a Blackwhip tendril directly from his mouth. 

The only drawback to Blackwhip is that its power is related to the user's emotions. Deku uses this to his advantage in Chapter 281 of the manga when he focuses his anger and hatred toward Tomura Shigaraki and creates a tendril powerful enough to restrain him. However, as first seen when Blackwhip emerges in Chapter 210, the power can sometimes be too much for Deku to control if his emotions are unstable.