Mokona, also known as Soel or White Mokona, is a small, white, rabbit-like creature that appears in Tsubasa: RESERVoir CHRoNiCLE as the fifth member of the main group. It was jointly created by the dimensional witch Yuko Ichihara and the sorcerer Clow Reed, specifically as a countermeasure for events foretold in Sakura's journey. Its age is indeterminate, reflecting its status as a magical entity. Mokona's most defining role is to enable the group to travel between dimensions, a power that is central to the story. It possesses a vast repertoire of abilities collectively referred to as its 108 secret skills, though not all are revealed. Among these are the ability to transport people and objects across worlds, to translate any language so that all members of the traveling party can communicate, to sense strong auras—most importantly the presence of Sakura's memory feathers—and to teleport items between itself and its counterpart, Black Mokona (named Larg), who stays with Yuko. Mokona's earring holds a mysterious power that can repel magical curses. Despite these capabilities, Mokona is not designed for combat and relies on the strength of its companions during confrontations.

In terms of personality, Mokona is cheerful, playful, and energetic. Its mischievous nature often shows through teasing, especially toward the stoic ninja Kurogane, which lightens tense situations. It is also deeply caring and attuned to the emotions of its companions, particularly Sakura, whom it treats as its primary charge. Mokona provides both emotional support and comic relief, and it occasionally offers moments of quiet wisdom about friendship and determination. Its primary motivation is to assist Sakura in recovering her memories and to fulfill the purpose for which it was made, though its bonds with the group become increasingly personal over time.

Mokona's role in the story is that of a guide and a logistical linchpin, as without its dimensional travel abilities the group could not navigate the multiverse. It also acts as a communication link back to Yuko's shop. Its relationships are integral to the journey: it shares a close, protective bond with Sakura; a playful, teasing dynamic with Kurogane; an affectionate rapport with the magician Fai D. Flowright; and a unique, twin-like connection with Black Mokona, which allows them to coordinate across dimensions. While Mokona does not undergo a traditional character arc of personal growth, its emotional depth becomes more evident as the series progresses—it evolves from a simple tool of travel into a sentient being that openly expresses grief, joy, and loyalty to its friends. Notable moments include using its dimensional expertise to bypass magical barriers, comforting Sakura in moments of doubt, and demonstrating courage in protecting the group. Throughout the series, Mokona remains a steadfast, beloved presence that combines mystique with charm.