May Jessica is the youngest member of the crew aboard the starship Sol Bianca. In the original OVA series, she was brought aboard by the ship's power, while in the later remake, Sol Bianca: The Legacy, she stows away on the vessel. April Bikirk takes an interest in helping May locate her parents on Earth, but they discover from an uncle and aunt that May's parents were killed by another group of pirates. May subsequently decides to remain with the crew as a permanent member, becoming the ship's chief engineer.

May is a lively and somewhat immature individual, often more interested in having fun than in completing her duties. She enjoys wearing frilly clothes and, despite her youth, holds a deep affection for the crew, whom she regards as her family. Because she has spent much of her life isolated, she sometimes views the world in simple terms. She also appears to have a crush on the young boy Rim Delapaz. Onboard the ship, she attends a holographic simulated school, though she is frequently preoccupied with play rather than her studies.

May serves as the ship's genius chief engineer, responsible for maintenance and repairs. For external work, she pilots an apple-green and red powered battlesuit, which is heavily armored and resembles a Landmate. She is also noted for piloting a mecha suit in combat situations. Her technical skills are vital to the operation of the Sol Bianca.

Her closest relationship on the crew is with June Ashel, with whom she shares a sister-like bond. The two are often left in charge of the ship when the other crew members are away on missions. May cares deeply for every member of the crew and is protective of them, though her youthful outlook means she can be somewhat naive. Throughout the story, she remains a loyal and capable member of the pirate band, growing more confident in her role as an engineer and pilot. Her abilities as a mechanic and her proficiency with the battlesuit make her an indispensable asset to the Sol Bianca.