Leviathan, a water mage dwelling in solitude within her Aquafall cottage after her older brother vanished, carries his staff as a reminder. Shyness and persistent self-doubt plague her, often causing her confidence to falter in difficult moments. Her driving purpose is uncovering her brother's fate, initially overlooking larger dangers to Aquafall. Leviathan wields water magic, its effectiveness tied to available water sources, a limitation in combat. She can transform into a water dragon, manifesting a sky-blue tail adorned with a pale green fin, matching wings, and horns.

Over time, she forges bonds with fellow dragon girls Bahamut and Jörmungandr, and the persistent fairy Syrup, who recruits them to combat Toripu invaders arriving via meteorites. Leviathan evolves from passivity to active participation within the group. She demonstrates this shift and resourcefulness by entering the dragon Yurlungur's body to eliminate Toripu causing his illness, creatively utilizing available liquids like barley tea for her magic when necessary.

Shared experiences, including the accidental destruction of a local tavern and collaborative battles against larger threats like Lucasites, strengthen her ties with Bahamut and Jörmungandr. Leviathan's caring nature surfaces through actions like assisting Jörmungandr's family during a mining cave-in and aiding an injured Fire Drake. Her journey illustrates growing self-assurance as she contributes to defending Aquafall while relentlessly pursuing clues to her brother's disappearance.