Sachiho Chiba, nicknamed "Sunny," is the captain of the educational battleship Kii and a third-year student at Sasebo Girls Marine School, hailing from Fukuoka City. Her given name, Sachiho, combines the characters for "sand," "thousand," and "sail," while her surname, Chiba, means "thousand leaves." She exhibits a cheerful, energetic, and positive demeanor, complemented by a resilient, never-give-up attitude and a strong, charismatic leadership that makes her popular among peers and crew. This optimism sometimes leads to impulsive actions, often tempered by her academically focused vice-captain, Keiko Nogiwa. Highly skilled in sports and martial arts like karate and kickboxing, she is also proficient in horseback riding. Academically, she excels in language learning and has no disliked subjects. Her preferences include blowfish and anpan, though she dislikes radishes. She favors the color red and the moth orchid, and lives by the personal motto “Natural and Unaffected,” reflecting her carefree approach. As captain, she energizes her crew aboard the Kii, a battleship of an unrealized design, and displays a competitive spirit, finding command challenges such as the flagship Musashi's situation "interesting." She has demonstrated martial prowess by defeating opponents armed with water guns or naginata. In drama CD extras, she participates in school parties and simulation games, losing one simulation to Mashiro Munetani and expressing surprise at the negotiation skills of Principal Munetani and student commander Moeka China. She also appears in the High School Fleet manga from volume 8, showing curiosity about the martial artist Mayumi Uchida. Her character draws inspiration from martial artist and actor Sonny Chiba, while her vice-captain is based on Yoko Nogiwa, Sonny Chiba's frequent co-star.