Duncan Rosenblatt: He is good-natured but jaded teen who feels like an outcast due to his mixed heritage and constant need to move. He has a short fuse, struggles to control his temper, and is fiercely protective of others who are marginalized, especially those who are bullied, He has a cynical outlook but is ultimately well-intentioned, seeking out other fringe dwellers who are less judgemental.

Jenna Shwartzendruber: She is intelligent and organized, but also has insecurities and can be surprised by unexpected situations, like Duncan revealing he's a half-kaiju. She deeply cares for Duncan despite her initial shock and rejection of him when she first learned his secret. She also has a precise preference for her coffee being 150 degrees.

Kenny Rodgers: He is loyal and kind nature, often being a supportive friend to Duncan, though he can be a bit naive. He is a nerdy outcast, obsessed with Kaiju lore, and harbors a one-sided crush on his friend Isabel. Despite being picked on by jocks, he remains caring and often a voice of reason, though he sometimes exhibits jealous tendencies, particularly concerning his friendship with Duncan.

Isabel Vasques: She is cynical, rebellious, and sarcastic teenager who is also secretly protective and caring of her younger brother. She initially struggles with her family's extraordinary abilities and resents their public image, but ultimately comes to accept and embrace them.

Margaret Rosenblatt: She is Duncan's mother and Belloc's ex- wife, whose main concern is provide a stable normal life for her son and looking out for his well-being. She still has unresolved issues with her nonhuman husband.

Belloc: He is an imposing, traditional, and ruthless leader of the Kaiju who wants his son Duncan to embrace his dragon heritage and conquer the Earth. He is a powerful and unforgiving ruler who sees mercy as a weakness, as seen when he kills a creature Duncan had spared. He values strength and lineage above all else, despite being the reason Duncan is a reluctant hero and sharing custody of him.