Runa Suruga, affectionately nicknamed Runa-chan, serves as a crew member in the Engineering Department aboard the destroyer Harekaze, reporting directly to Chief Engineer Maron Yanagiwara. Her appearance is distinctive: long violet hair styled in pigtails secured with bright orange ribbons, golden eyes, and the standard uniform of Yokosuka Girls' Marine High School, standing 152 cm tall. She possesses a bubbly, eccentric personality characterized by notable forgetfulness and high excitability, frequently creating humorous situations. Moments of insecurity surface, such as comparing her physique to peers during bath scenes. Despite her scatterbrained nature, she demonstrates genuine kindness and persistent dedication to her engineering duties. Academically, she initially entered the school as an alternate after missing her exam results; her dramatic reaction—jumping into the winter sea—required rescue by Satoko Katsuta. Hailing from Hayama Town, Miura District, Kanagawa Prefecture, her childhood was shaped by her father’s profession as a ship designer. She intuitively absorbed machinery and thermodynamics knowledge by frequently copying his blueprints, forming the foundation for her technical qualifications: Junior Third-Class Marine Engineer (Mechanic), First-Class Junior Boiler Technician, and Standard Boiler Welder. She communicates complex technical concepts non-verbally with Yanagiwara, often using tools like spanners for collaborative work. Socially, she forms one-quarter of a tight-knit group with Reo Wakasa, Sakura Ise, and Sora Hirota, regularly playing card games and mahjong during downtime. Her consistent confusion over mahjong rules provides recurring amusement for the group, highlighted in OVA episodes where tile errors prompt playful teasing. Personal preferences include favorite foods like okonomiyaki and sweet red bean jelly, a dislike for nameko mushrooms, and a signature catchphrase referencing all four seasons. Across all narrative media, including the movie, she maintains her engineering role during key events like the inter-high tournament festival and the sea fortress infiltration. Her technical skills are vital to ship operations, exemplified by an unfinished side project to convert a boiler into a tandoor oven at Megumi Uda's request. Character-defining quotes such as "Humans? I quit being one!!!" perfectly encapsulate her whimsical spirit.