While Kana and Thomas deliver aquarium materials for the Vicarstown Fish Day, it's up to steady Percy and Nia to deliver the fish themselves. However, Nia gets a wobbly wheel, inciting Percy to ask Kana for a switch so she can help Nia and speed up the delivery. Once Nia is fixed, she's raring to go, but Kana unexpectedly wants to slow things down to keep the fish safe. Could this quarrel spell doom for the delivery or allow these engines to learn something they never realized about each other?