Black first met Musha when he was only five years old. After Black's dreams caused him to daydream and unable to focus, Musha became attracted to him and quickly bit down on the young boy's head, much to his friend Cheren's horror. After helping him capture a wild Rufflet, Musha offered to be captured by Black and joined his team after the boy accepted.
Musha was first seen in Choices with his Trainer, Black, and his Braviary, Brav. When Black went to rescue a runaway Tepig, he used Musha to scout out a wild attacking Sewaddle, allowing him to defeat it. Musha, along with Tep, and Brav, were used against Hiker Andy, where they managed to defeat his three Pokémon in a Triple Battle. Musha was used to help Black find out a way to stop the fire that Andy's Cottonee had accidentally started.
In Battle at the Dreamyard, Musha flies away from Black after sensing a powerful dream. With the help of Professor Fennel, Black and White find Musha in the hands of some Team Plasma Grunts. When Black tries to figure out a plan to defeat them, his brain overloads from trying to think of something that doesn't involve the Pokémon League. Musha becomes attracted to this overflow of dreams and flies from the grasp of the Grunts and goes back to Black. With the help of Musha, Black manages to defeat the Grunts and drive them out.
Musha is later used in Black's Gym battle against the Nacrene City Gym Leader, Lenora. He fought her Stoutland briefly before being sent back into his Poké Ball by its Roar. Later, after Brav was knocked out and the two Trainers only had one Pokémon left, Musha was sent out to battle Stoutland again, this time defeating it with Zen Headbutt.
Sometime later, Musha is used in Black's Gym battle against the Gym Leader of Driftveil City, Clay. Musha battles Clay's Palpitoad and is trapped by its long tongue. Eventually Musha manages to knock out Palpitoad with a Zen Headbutt but faints in the process.
After battling N, Musha was revealed to have only followed Black's orders because his dreams were considered tasty to Musha and kept him fed. After the taste of Black's dreams changed over the course of his adventure, Musha decides to leave Black.