Hakase Yukawa is a recurring character known as a friend of the boy Shota. The name Hakase translates to doctor or professor in Japanese, and he is depicted as a young but highly knowledgeable inventor with a strong passion for science. Throughout the story, he creates and presents a variety of novel inventions, showcasing his extensive understanding of scientific principles despite his age. His appearance is distinctive: he is bald and is almost always seen wearing a gown that covers his hands entirely. In terms of personality, Hakase is generally amicable and well-mannered. Unlike other characters who sometimes bully Shota and the ghost Q-taro, he gets along with most of the cast. He is an honorific character who consistently speaks politely, using formal titles even when addressing his close friends, and often adds a particular verbal tic to the end of his sentences. Despite his intellectual gifts, he has a notable weakness: he suffers from severe motion sickness, to the point where merely looking at a picture of a bus can trigger his condition. His role in the narrative is primarily that of a supportive friend and a source of scientific solutions or commentary. Regarding his background, there is a specific but limited setting where his surname is given as Yukawa, which is thought to be inspired by a famous Japanese physicist. In terms of development, one later adaptation portrays all of his business ventures in the future as having failed. Hakase has no supernatural powers or ghost abilities, but his notable talent lies in his capacity to invent and apply scientific knowledge, which distinguishes him from the other primarily school-aged characters and serves as his key contribution to the group.