Rakko, whose Japanese name means "sea otter," is a strong hunter specializing in high-risk monster-slaying missions known as "subjugation work." His capabilities command admiration from others.

He possesses pale yellow fur, fluffy in texture, with black ears and limbs. A distinct cross-shaped scar marks the area over his right eye. He always carries a white cloak and a large greatsword strapped to his back.

Rakko blends bravery with a nurturing nature. Despite being the top-ranked combatant in the United Assassins Association, he harbors a notable sweet tooth, often indulging in desserts with childlike enjoyment. Conversely, he struggles with online fighting games. He acts as a mentor, especially to Hachiware, demonstrating care through shared meals, guidance, and providing car transportation for Chiikawa and Hachiware.

Functioning as a brother figure within the group, particularly towards Chiikawa and Hachiware, Rakko encourages growth, like urging Chiikawa to try disliked foods such as broccoli. His reliable and kind nature, shown through treating others to meals and offering supportive advice, fosters peer admiration.

Significant emotional depth surfaces during his visits to a memorial park statue, where he once vowed to become stronger. While the reason for this vow remains undisclosed, he later returns to express joy at being called "sensei" by Chiikawa and Hachiware, indicating the importance of this recognition.