Buzam A. Calessa, almost always referred to as B.C., serves as the second-in-command of the battleship Nirvana. She is a woman of 28 years, standing 173 cm tall, with a stern and businesslike demeanor that defines her public persona. B.C. is a dedicated workaholic who is rarely seen away from the ship's bridge, where she constantly monitors data and evaluates the crew's performance. She is a highly skilled tactician who issues orders firmly and decisively, acting as the primary relay between the enigmatic captain, Magno Vivan, and the rest of the crew. Her role is central to the ship's operations; she coordinates all assaults from the bridge and is also proficient in close-quarters combat, notably wielding a whip with great dexterity.

Despite her austere and commanding exterior, B.C. genuinely looks after the welfare of the crew, demonstrating a caring nature beneath her strict façade. This dedication, however, is complicated by a series of secretive actions early in her story. She is observed covertly removing a data disc from the bridge's database, hinting at a hidden agenda that stands in stark contrast to her position of trust.

The truth behind these actions reveals a profound deception. B.C. is not a woman from the planet Mejeiru as she appears, but is actually Tenmei Uragasumi, a high-ranking male intelligence officer from the opposing planet of Taraak. To execute his infiltration of a female-dominated society, Tenmei underwent a complete sex change and uses a device on a green necklace to simulate a feminine voice. This shocking revelation re-contextualizes her every action, transforming her from a trusted subordinate into a deep-cover spy.

However, B.C.'s development is defined by how her loyalties shift. Despite being planted to gather intelligence on the women of Mejare, the bonds she forms while living as a member of the Nirvana crew become genuine and powerful. Her connection with Captain Magno Vivan is particularly strong; when her true identity is exposed, it is this relationship that determines her fate. Ultimately, Magno forgives the spy, but on the condition that she remain B.C., effectively choosing to value the person she has become over the man she was.

This pivotal development allows her to continue her role as a commander, leading the Nirvana with undivided loyalty in the final battles. One of her key relationships in this later period is with the pilot Bart Garsus, who develops romantic feelings for her. Even upon discovering her past as a male spy, Bart remains unaffected in his affection and continues to pursue a relationship with her.