Prior to the start of the Black & White arc Dake-chan was one of the many Pokémon Team Plasma had liberated from people and were planned to release into the wild after N's victory. Whi-Two was excited to see so many new Pokémon but noticed a Poké Ball among the group. Angered at the presence of such an evil thing Whi-Two goes to remove it, before discovering that the Poké Ball was in fact a Foongus. Frightened, she throws the Mushroom Pokémon, and then apologizes for the mistake. Whi-Two then gives Foongus the nickname Dake-chan, while Rood advises her not to do so, as she will become to attached to him, making his release into the wild a harder experience.
Dake-chan first appeared in A Difficult Parting, along with many other Pokémon Team Plasma had liberated. Whi-Two, alongside other Team Plasma Grunts, where making an escape just after Team Plasma's defeat, with the liberated Pokémon being released after. Whi-Two wanted to bring all of the Pokémon with them, not wanting to leave so many friends behind. Anthea and Concordia decide to allow Whi-Two to pick one of the Pokémon to take with her and she picks Dake-chan, as she gets along with him the most. They then make their escape from N's Castle, avoiding arrest.
Two years later, Whi-Two enters the Aspertia City Trainers' School, bringing Dake-chan with her. With the arrival of a new student, Cheren has the students compete in a tournament battle with one side for the boys and the other for the girls. Whi-Two uses Dake-Chan throughout the tournament, eventually winning the final battle against a Sigilyph. Whi-Two finds this surprising as she was trying not to win for fear of standing out. Being the winner, Whi-Two receives a Pokédex.
In PS529 Whi-Two and Lack-Two head to Pledge Grove to collect data on their Pokédexes. After Lack-Two attempts to get too close to Whi-Two, Dake-chan quickly attacks with Sweet Scent forcing Lack-Two away. The Sweet Scent then attracts a wild Keldeo, which swiftly attacks the two Trainers, throwing them off a cliff. Lack-Two manages to keep Whi-Two from falling, but was unable to do the same for Dake-chan. Whi-Two refuses to leave without the Mushroom Pokémon, and Lack-Two goes down to save him. Reassuring Dake-chan that he does not want to cause harm to Whi-Two, Dake-chan allows Lack-Two to help.
Dake-chan is later used as the partner for Whi-Two's part of Foongus Girl at Pokéstar Studios. Despite the lines being scripted, Dake-chan participates in a real battle against Brycen-Man's Pawniard, taking it out with a single Giga Drain. Before the battle can continue the Mecha Tyranitar starts to attack everyone in sight, and is quickly stopped by Lack-Two's Dewott.