Rakko, a sea otter whose name means "sea otter" in Japanese, sports pale yellow fur contrasted by black ears and limbs, accentuated by fluffy texture and a distinct cross-shaped scar over his right eye. He is always shown bearing a white cloak and a greatsword strapped to his back. Renowned for exceptional physical strength and hunting prowess, Rakko specializes in high-risk monster subjugation. He holds the top rank within the United Assassins Association rankings, yet performs poorly in online fighting games. A notable sweet tooth defines him, marked by a particular fondness for desserts and sweet treats. He owns a personal vehicle, which he has used to transport Chiikawa and Hachiware multiple times. Rakko serves as a mentor to Hachiware, actively training him to improve his abilities, and encourages Chiikawa in personal challenges like consuming disliked foods such as broccoli or practicing singing. His personality blends bravery and reliability with underlying kindness, frequently sharing meals and offering guidance to others. He displays deep respect for a memorial park statue, visiting it for quiet reflection. During one visit, he confided to the statue about a past vow to become stronger. The moment Chiikawa and Hachiware addressed him as "sensei" elicited an ecstatic reaction, prompting him to immediately return to the statue to report this development. While Rakko's full backstory remains largely unexplored, these memorial site interactions provide significant insight into his personal history and emotional motivations. His consistent role positions him as a protective older brother figure within the group, offering both practical support and mentorship.