The three swordsmen wander through the Monster Association Headquarters taking care of monsters when they run into Devil Long Hair, who recites some haiku poems.
Upon seeing Devil Long Hair's attractive looks, Okamaitachi is immediately infatuated by him but tries to resist it due to such a relationship being forbidden love. Iaian, unsure of the opponent's power, tells Okamaitachi to use his Air Blade technique to see how Devil Long Hair would respond. However, both Iaian and Bushidrill see their comrade's hesitance and give him an annoyed stare. Bushidrill tells Okamaitachi to get it together and goes so far as to call him a dumbass. Okamaitachi mocks Bushidrill by asking if he's jealous, and the swordsman replies by asking if he can cut Devil Long Hair up. Iaian tells them to calm down and reminds them of the severity of the situation they're in.
Agreeing with his comrade's words, Okamaitachi's resolve becomes clear, and he tells Devil Long Hair that he's unable to "reciprocate his feelings". The monster tells him that this news strikes him like "a bolt from the blue". The swordsman then prepares his Air Blade, a long-range attack in the form of a huge blade of wind. Bushidrill displays some jealousy over such a divine technique that's impossible to replicate. Unfortunately for the heroes, Devil Long Hair is not afraid, telling the A-Class heroes they know nothing of the terror of his hair, and blocking the long-range attack with his hair.
Iaian is shocked that the monster was able to stop the air blade with his long hair. Meanwhile, Bushidrill warns Okamaitachi of a surprise underground attack. Okamaitachi looks behind him, and sees a strand of hair about to attack him, but Bushidrill slices the hair before it can strike Okamaitachi. The swordsman thanks his comrade, and Bushidrill comments on Devil Long Hair's strength. Iaian assesses the strength of their opponent, the sharpness of his hair, the dexterity of the hair and its capacity to sneak through the smallest cracks of their armor and body parts. Iaian also theorizes that Devil Long Hair's hair can also perform piercing, binding, restraining, throwing, and severing attacks. However, Iaian is confident he can cut him in half even while he's guarded.
Devil Long Hair scoffs, and tells them they'll drown in his hair. The monster stabs his hairs underground and all attack the swordsmen. Iaian unsheathes his sword, closes his eyes, and pares the strands of hair. The swordsman then tells his partners to not follow the hairs with their eyes, but to feel the murderous aura emanating from the hair and counter with their reflexes. Devil Long Hair attacks with several more hair strands, while Iaian looks at what they're up against: approximately 100,000 strands of hair against their three blades, and tells Okamaitachi and Bushidrill to not let their guard down. The three swordsmen hold their own against the hair attacks, although they quickly become trapped and entangled by the hundreds of hair strands.
They wonder what their master would do in such a situation, and they reminisce on a conversation they had with their master before. In this flashback, Iaian asks his master how they should interpret the prophecy Madame Shibabawa warned of, and what they should do against a monster so powerful that it couldn't be defeated by humans. Atomic Samurai replies by saying that they will have to become beyond a human. Iaian reflects on these words, invigorated by them and determined to follow in the footsteps of other heroes such as Tatsumaki, Pig God, and Atomic Samurai who've surpassed human limits. Okamaitachi and Bushidrill agree, and the three heroes pounce into the air, prepared to eliminate Devil Long Hair.
An unseen battle takes place between the three swordsmen and the mysterious being, and after this hard-fought battle, Devil Long Hair's hair has been pared. The monster goes on to say that his Achille's heel is his hair, and he collapses, marking victory for the three swordsmen. Okamaitachi is amazed they won by only rushing him and cutting his hair. Iaian agrees, saying that Devil Long Hair was a terrifying opponent with great offense and defense. Bushidrill adds onto this by saying that it was a close battle, and by themselves, they wouldn't have been able to keep up. He also wonders if there are other powerful monsters like Devil Long Hair, and if so, it would be tough to deal with them. Regardless, Iaian says they won't have to worry about their master.
After fighting Devil Long Hair, the three A-Class swordsmen continue to venture throughout the labyrinth of the Monster Association, when they come across Evil Natural Water, who manages to defeat all of them and put them in near-death states.
- This is Iaian's first battle that has not been interrupted and finished by another hero.
- Devil Long Hair's defeat is an example of an ironic defeat, as the hair that he loved so much is pared by the three swordsmen.