Kuguru Uki is a 6th-year elementary student at Aibo Academy, classmates with Gao Mikado and childhood friend Baku Omori. Her deep expertise in card mechanics and vast knowledge of various cards earns her the nickname "The Library"; she consistently uses a tablet to access and display card information during matches. She serves as a foundational member of Team Balle du Soleil alongside Gao, Baku, and Kiri Hyoryu, acting as the team's dedicated card analyst who provides strategic insights and deck support. Physically, Kuguru sports purple hair styled in two small pigtails extending through functional circular lamps on her head. She wears red-framed circular glasses and a white long-sleeved outfit resembling a Japanese sailor uniform with teal accents and a fuchsia ribbon, extending into a skirt-like design paired with white thigh-high boots featuring matching teal accents. Personality-wise, Kuguru exhibits a supportive and encouraging demeanor, particularly towards Gao. She demonstrates assertiveness when needed, such as blackmailing Baku to build a viable deck for Gao. Her interactions with Baku occasionally suggest deeper affection, shown through intense reactions to his dismissive comments about romance and a celebratory hug after Gao's victory over Kyoya. She displays persistent hostility toward Ozon-B, often threatening him with extreme measures like chainsaws. Her narrative role centers on non-combatant support, focusing on analytical and emotional backing rather than frequent buddyfighting. During the Gaen Cup arc, she helps maintain team morale amidst revelations about Purgatory Knight's identity. In Season 2 (Future Card Buddyfight 100), her prominence lessens as the narrative shifts toward Gao, Tetsuya, and Zanya Kisaragi, though she continues contributing to deck construction and team strategy. Her documented buddyfight record includes a Season 1 victory against Baku (disguised as Shusui Kanahebi) and a Season 2 loss to Zanya Kisaragi. Kuguru's relationships are defined by loyalty and occasional comedic tension. Her childhood connection with Baku forms a recurring dynamic blending camaraderie with subtle romantic undertones. She remains a steadfast ally to Gao, leveraging her knowledge to advance his capabilities as a buddyfighter. Her role emphasizes intellectual support and group cohesion, positioning her as a stabilizing force within Team Balle du Soleil.