Yanyan commands the antagonistic Dirt Cheap Trio alongside subordinates Dasainen and Tonmentan. Her core mission drives her to gather scattered Divine Puzzle pieces, seeking entry into the elite Oshaka Academy based on her conviction that she and her team descend from Priest Sanzo's lineage, despite unverified heritage.

She wields a Sea Dragon Whistle shaped like Tatsunoko Pro.'s mascot, using it to summon Ryuko, a dragon girl dwelling at Otamaga Pond's depths. Upon summoning, Ryuko transforms into the organic Den-Den Mecha, resembling a snail. This mecha, equipped with visible ribs and breast-shaped buttons Ryuko dislikes activating, transports the trio globally and engages their foes.

During a puzzle piece hunt in Italy (episode 16), Yanyan develops romantic feelings for the gondolier Wanita. This sparks rivalry with Ryuko, who also becomes infatuated. Their competition for Wanita escalates into a feud where they break his guitar, inadvertently revealing his true form as an alligator yokai empowered by a Divine Puzzle piece. Both Yanyan and Ryuko are left heartbroken after the confrontation.

Yanyan leverages her alliance with Ryuko for strategic gains, notably deploying Relief Mechas starting in episode 13. Ryuko's magical breath enlarges these mechas, themed after yokai previously defeated by the episode's antagonist and powered by reclaimed puzzle pieces, forming the trio's main counterattack. Despite their cooperation, Ryuko sometimes responds with snark or teasing.

After the Dirt Cheap Trio's conclusive defeat, Yanyan's ultimate fate remains unrecorded. While the Den-Den Mecha resurfaces in later Time Bokan spinoffs, it displays no sign of retaining sentience linked to Ryuko or any connection to Yanyan.