Noi Crezant is the lizard familiar bound to Yuuhi Amamiya, the Lizard Knight. He manifests physically, usually perched on Yuuhi's shoulder. Ordinary humans cannot see or hear him unless they have a connection to the princess or the Beast Knights' conflict, a selective invisibility maintained in schools and public spaces. His physical state directly reflects Yuuhi's health, becoming visibly ill when Yuuhi catches a cold after falling into a river. While actions like being thrown from windows or vaulted off bicycles cause no lasting harm—he simply reappears unscathed—deliberate violence inflicts genuine pain, making him scream.

He adheres strictly to a code of chivalry and earnest duty, prioritizing the princess's protection and Earth's preservation from the Biscuit Hammer. He initially opposes Yuuhi and Samidare's shared goal of destroying the world, actively trying to guide Yuuhi onto the traditional heroic path. His guidance involves delivering exposition on the conflict, such as the contractual wishes granted to Beast Knights upon formally accepting their roles. During Yuuhi's confrontation with his dying grandfather, Noi critically intervenes, urging Yuuhi to use his Beast Knight wish for healing despite Yuuhi's unresolved trauma and resentment. This highlights Noi's persistent efforts to steer Yuuhi toward morally aligned decisions, even against resistance.

His knowledge encompasses the broader mythology of the Beast Knights' conflict, including references to a prior failed campaign against the Mage where he faced defeat. He deliberately withholds strategic information, such as the existence and significance of the Mythical Beast Knights, promising full disclosure only if Yuuhi achieves specific milestones like surpassing another knight. He also warns of potential internal threats, notably advising caution about the Owl Knight. His role evolves from a stern advisor to a more complex figure balancing his duties with protective watchfulness over Yuuhi's growth. He provides comedic relief through exaggerated reactions to physical mishaps, while consistently anchoring exposition and thematic exploration of loyalty and heroism.

His relationship with Yuuhi is defined by friction and reluctant guardianship. He frequently lectures Yuuhi on responsibility and chivalric ideals, openly criticizing his nihilism and initial childish tendencies. Tensions stem from their opposing stances on world destruction, yet their contractual link binds them. Over time, Noi develops a nuanced commitment to Yuuhi's development, acknowledging his strategic intellect and latent potential even while disapproving of his ultimate goals. This duality positions Noi as both an antagonist to the protagonists' secret plans and an unwavering, if conflicted, ally in the larger battle against the Mage Animus.