Cap is Kakeru Nohara (Striker)'s pet parakeet. Before Striker awakened as a pyroxene card battler and obtained the green pyroxene stone, Cap could only mimic phrases without understanding human speech. The stone's power granted Cap full speech comprehension and the ability to talk, consistent with other pets bonded to the chosen battlers' stones.

As part of the group of pets connected to the pyroxene holders, Cap regularly joins their collective activities and discussions. These interactions involve the other pets—Aibou (Bashin's mouse), Okyou (J's cat), Pink (Suiren's chameleon), and Nanarin (Meganeko's dog)—often providing comic relief or minor commentary on the human characters' actions. Cap appears consistently across all 50 episodes of the series, including the *Burning Soul* New Year special.

The character receives its most significant narrative focus in episode 37, "The Spirit of Aibou's Group," which centers on the pets' perspectives and group dynamics. Cap also accompanies the main cast to the beach in episode 44, participating in the depicted training and recreational activities. While not independently driving major plotlines, Cap contributes to the series' lighthearted tone through interactions with the other pets and occasional reactions to Striker's enthusiasms, particularly concerning soccer or the idol My Sunshine.