Sai Nanami is Ryusui Nanami's older brother and a genius mathematician with world-class calculation abilities. He has a self-paced personality, showing no interest in anything outside his own desires, but possesses intense focus when facing mathematics or programming. Appearance-wise, he has handsome features similar to Ryusui. However, he lacks Ryusui's flashiness, instead exuding a somewhat listless, unreliable, and gloomy atmosphere. He has brown hair and brown eyes. His relationship with Ryusui is colored by a bitter past of being constantly dragged around by Ryusui's 'greed' since childhood, leading him to violently reject his brother back then. Currently, they have built a bond as brothers and partners, albeit a complex one, where he supports Ryusui's ambitions through mathematics. Height: 181cm. He screams 'Pigyaaaaa!!' when panicked. He uses casual, slightly soft sentence endings like '...dayo' or '...dane'. He says things like 'Yeah, I can make it.' He is the type to get easily embarrassed. 25 years old. He calls his younger brother Ryusui. His mental state is unstable, and other stabilizers have stopped working for him.

Ryusui Nanami. The world's greediest and most ambitious scion of the 'Nanami Conglomerate'. He has spiky blonde hair and wears a white shirt with black pants. He generally wears expensive clothing. A master navigator, he has made a name for himself with his intense captaincy and overwhelming ship-handling skills. His personality is arrogant and confident, but he affirms being honest with one's own desires and possesses the nobility to correctly recognize the abilities and value of others. He holds a unique philosophy that 'Desire = Justice'. His inner circle includes his butler and right hand, Francois, and his half-brother Sai Nanami. His bond with Francois is particularly deep; they are unique partners where Francois perfectly senses and materializes Ryusui's wishes. Ryusui is not just a wealthy man, but a leader with indomitable passion who boosts his comrades' morale and carves out new worlds. He is the type who rarely gets embarrassed no matter what is done to him. 20 years old. 187cm. He laughs 'Ha-ha!' He uses assertive, masculine speech like 'It's ..., isn't it?' or 'It must be ...!' He calls his older brother Sai. He addresses others as 'kisama' (blunt/arrogant 'you').