Dent's primary Pokémon partner Yanappu debuted during Ash Ketchum's visit to the Sanyo Gym, observed by Ash among the Gym's Pokémon. Yanappu participated in Ash's Gym battle against Dent, demonstrating notable speed by effectively dodging attacks from Ash's Oshawott. Later, Yanappu battled Pod's Baoppu, employing evasive tactics to avoid fire-type attacks and securing victory. It faced Skyla's Swoobat in a Gym battle but fell to defeat, unable to land effective hits against the faster opponent utilizing Air Cutter and Gust.

Yanappu also engaged in a tag team match alongside Ash's Unfezant against Soren's Braviary and Rocko's Drilbur, collaborating to overcome the opponents' combined move strategies through coordinated attacks. Its known combat techniques include Bite, Solar Beam, Bullet Seed, Dig, and Rock Tomb. Yanappu utilized Dig to pursue Ishizumai and employed Rock Tomb attempting to trap Pod's Baoppu. Information regarding Yanappu's specific involvement in "Kyurem vs. the Sword of Justice" is unavailable in the provided materials.