Tigerlily, called Zuruko in Japanese, emerges as Yuna's cousin midway through Season 2. Their relationship balances love and hate, marked by constant clashes yet underlying mutual care. Yuna resents Tigerlily's coercion through blackmail and intimidation to enforce chores, dubbing her "Tiger the Tyrant." Despite a cheerful facade, Tigerlily's harsh demeanor intensifies conflicts. Yuna retaliates by disrupting Tigerlily's naps or exploiting her severe lightning phobia.

In Season 3, Yuna and Stitch move in with Tigerlily in Okinawa's New Town. Tigerlily's role expands, showing slight mellowing through marginally friendlier behavior while still enforcing Yuna's chores. She justifies her strictness as modeling responsibility, citing Yuna's academic struggles to assign tasks and threatening reports to their grandmother.

Beneath their friction, Tigerlily genuinely prioritizes Yuna's safety, sacrificing her own desires to protect her—though she later leverages these acts to demand "repayment" favors. Fleeting vulnerability surfaces, like Yuna hugging her affectionately. Tigerlily reacts with palpable anger or dread to age-related remarks. Yuna's deep-seated fear manifests when a terror-inducing entity takes the form of a dinosaur resembling Tigerlily.