Junior, also known as Kato Takigawa Jr. or by the nickname Shou, is a supporting character in the Martian ocean setting. He is identifiable by his distinctive appearance, which includes pink hair cut to ear length and purple eyes, often seen with accessories such as a headband, gloves, boots, and a necklace. He is a teenage member of the crew aboard the Ship of Aurora.

Junior holds a deep-seated ambition to pilot a Round Buckler, the series' mecha units, and to contribute more directly to the ship's operations. This eagerness is a core part of his personality, sometimes leading him to act on his desires without full authorization. In a notable incident, he takes an RB out for a ride without obtaining permission, an act of impulsive courage that results in him being captured by the Earth Forces.

His role within the story is primarily as a fellow crew member of the pirate submarine, working alongside the protagonist Gram River and others. Throughout the series, his determination to fulfill his dream demonstrates clear development. His persistence pays off when he is eventually appointed as a diver for a new Round Buckler, marking the realization of his long-held aspiration to become an active pilot in the field. This progression from an aspiring member to a qualified diver represents a significant step in his personal journey aboard the Aurora.