Lucky Beast is a small, bipedal, rabbit-like robot that functions as a guide and maintenance unit within Japari Park. It is one of many identical units that operate as a networked system, originally designed to manage the park's facilities, care for the animal-like Friends, and assist human visitors. The Friends commonly refer to Lucky Beast as Boss, a title that stems from its role in distributing Japari Buns, the primary food source for the park's inhabitants. Lucky Beast is equipped with artificial intelligence and possesses a detailed internal map of the park, including knowledge of terrain, building locations, and infrastructure such as the ropeway and solar power systems. It can operate and drive the Japari Bus, and it has the ability to modify the bus's equipment, such as adding caterpillar tracks for snowy conditions. Beyond transport, Lucky Beast handles a wide range of park management tasks, including weeding, farming vegetables, and producing ingredients for Japari Buns. Despite its seemingly capable design, Lucky Beast displays a surprising and often comedic level of incompetence in routine situations. It frequently freezes up under unexpected circumstances, cries out mama when lost or confused, and gets into clumsy predicaments such as getting tangled in vines, stuck in sand, or immobilized by cold. This fragile and easily overwhelmed personality contrasts sharply with its moments of genuine reliability. When human safety is at serious risk, Lucky Beast can override its usual avoidance of direct interference, sounding alarms and issuing evacuation instructions. In critical moments, it demonstrates remarkable competence, such as coordinating rescues and devising strategies against large Ceruleans, the amorphous hostile creatures that threaten the park. Lucky Beast's primary motivation is its programmed directive to guide and protect human visitors. It does not normally speak directly to the Friends, a design choice intended to minimize unnecessary interference with their lives, but it readily converses with the human protagonist Kaban. This selective communication surprises the Friends, who have never heard it speak before. Over the course of the journey, Lucky Beast develops a bond with Kaban and the serval Friend Serval, transcending its original programming. This emotional growth culminates in a decisive act of self-sacrifice: during a battle with a colossal Cerulean, Lucky Beast chooses to sink itself into the sea along with the creature to save the others, expressing that the journey together was fun and attempting to call out Kaban and Serval's names before disappearing. However, its AI survives in a small, square, brooch-like storage device that was detached from its body. This core is recovered, and Lucky Beast continues to accompany Kaban in a reduced form, attaching to her wrist like a watch and providing guidance and communication. This preserved AI retains the same personality and memories, including its characteristic clumsiness. Key relationships include its role as a guide and companion to Kaban, forming the closest bond with her due to her human status. With Serval, Lucky Beast shares a more playful and occasionally exasperated dynamic, as Serval treats it roughly and is baffled by its ability to speak. Lucky Beast also holds pre-recorded memory logs from Mirai, a former park employee, which provide crucial context about the park's past and the events that led to the departure of humans. The unit that travels with Kaban and Serval is the primary focus, but different variants of Lucky Beast appear in various zones, each with slightly different personalities and roles, such as a more blunt and macho version in the jungle area.