Kakeru Yuiga is an eighteen-year-old young man who serves as one of the central figures aboard the Norn, often acting as the de facto leader and strategist for the group of superpowered individuals. His physical appearance is notable for his blond hair and metallic grey eyes, a look complemented by his typical attire and a distinctive earring he always wears on his left ear. He was born on July 25th, making his zodiac sign Leo, and stands at 176 centimeters in height with B type blood.

At first glance, Kakeru presents the demeanor of a kind, cheerful, and trustworthy young man who is quick-witted and proactive. He uses his natural optimism and individual approach to bring the other members together, proposing ideas such as the pairing system to help the group function more smoothly. However, this pleasant exterior masks a more complex inner nature. Due to his sharp intellect, he possesses a manipulative and calculating side, leading some of the crew to view him as a schemer or a wicked, "haraguro" person. This is further complicated by his personality as a natural sadist, though it is an unconscious trait; he has a tendency to corner people, particularly Senri and Masamune, without any malice or awareness of doing so. His leadership style often involves using language as a tool for guidance and control, establishing him as a firm presence despite his age not being the oldest on the ship.

Kakeru's motivations are deeply tied to the wellbeing of the Norn and its inhabitants. He took the initiative to reveal his ability to control plant life publicly because of its practical use in generating crops for sustenance, thus ensuring the group's survival. Beneath his carefree smile, he hides a painful past and a history that continues to haunt him. He was taken in as a child by his adoptive father, Shirou Yuiga, who valued him specifically because he was already an esper. The earring he treasures as a memento is, in reality, a tool implanted by his father to induce brainwashing, a fact that represents a significant betrayal and contributes to his lingering trauma and distrust. He despises falling ill, as it reminds him of the weakness of his childhood self.

In the story's narrative, Kakeru is primarily paired with Koharu, for whom he is a selectable hero. Their relationship is a key aspect of his character development. He enjoys teasing Koharu, but unlike his interactions with others, this tendency often leads him to feel a sense of guilt due to her innocent and straightforward nature, creating a dynamic where her genuine kindness naturally counters his more cynical traits. His connection with the other male crew members is also significant; he shares a room with Masamune to prevent conflicts and relies on his capabilities, while his treatment of Senri is notably harsher, openly treating him as a sort of "toy". Some of the female members, such as Nanami and Mikoto, remain wary of him, finding his hidden nature difficult to fully trust.

His notable ability is the manipulation of plant life, often referred to as controlling "greenery" or the color "blue". This power allows him to summon and command any form of flora, from common plants to trees, making it both incredibly stable and overwhelmingly powerful in practice. This talent was so useful in his original village that he was welcomed and cared for by the residents, contrasting sharply with the manipulation he experienced from his father.

Throughout his arc, Kakeru's development revolves around the struggle between his genuine desire to protect others and his ingrained habit of controlling situations from the shadows. His journey with Koharu involves confronting his painful past, particularly the brainwashing by his father, and learning to accept genuine emotional bonds without manipulation. By the end of his story, he seeks to achieve a balance between his role as a strategic leader and his own personal need for connection, moving from a state of being controlled to one of self-acceptance.