Javelin is a Royal Navy J-class destroyer and one of the main protagonists. She possesses a slender frame and a medium bust, standing approximately between 148 and 154 centimeters tall. Her long lavender hair is tied into a messy high ponytail with a dark-blue ribbon, and she has bright aqua-colored eyes. A small mini crown rests atop her head.

She wears a purple hooded scarf wrapped around her neck, featuring bear ears and a red ribbon. Her attire consists of a white blouse with jagged ends, blue laces, and yellow buttons, complemented by an anchored-chain that dangles at her side. Over a frilled black skirt, she wears a red and blue plaid skirt, along with black socks and blue boots. On her right arm, she wears a single white glove adorned with a red ribbon, and a blue bracelet is on her left wrist.

Javelin is nice, friendly, and energetic by nature. Some depictions suggest she occasionally entertains rather dirty thoughts.