Hidetoshi Dekisugi is a recurring character in the Doraemon series, known for being a classmate of the protagonist, Nobita Nobi. As a student in a typical Tokyo elementary school, he stands out as the polar opposite of Nobita in nearly every measurable way. His name itself is a pun on the Japanese word dekisugiru, which means to be overly excellent or accomplished, a direct reflection of his core character trait.

Dekisugi is defined by his exceptional and well-rounded abilities. He consistently achieves perfect scores on all academic tests and excels across a wide range of subjects, demonstrating a particular interest in astronomy and philosophy. Beyond the classroom, his talents extend to physical activities, where he proves to be a skilled athlete in sports like baseball and soccer. He is also proficient in artistic pursuits such as realistic drawing and painting, as well as practical skills including cooking, household chores, and even magic tricks. This combination of academic brilliance, athleticism, and artistic talent makes him a widely admired figure among both teachers and students.

Despite his vast array of talents, Dekisugi’s personality is characterized by humility and kindness. He never boasts about his abilities or looks down on others who are less capable. Instead, he is consistently polite, levelheaded, and rational, often approaching situations with a scientific and logical mindset while dismissing superstition. This compassionate nature is most evident in his treatment of Nobita. While Nobita often views him as a rival, particularly for the affection of their friend Shizuka Minamoto, Dekisugi regards Nobita as a friend. He has been shown defending Nobita from bullies, emphasizing that a person's value to society is more important than test scores, and even discreetly helping Shizuka bake a birthday cake for Nobita. On one occasion, when a jealous classmate named Gariben tried to sabotage him with prank calls, Dekisugi responded by offering to help him with his studies instead of seeking revenge.

Within the story's dynamic, Dekisugi's primary role is often that of a gentle rival and a source of knowledge. Nobita frequently feels envious of Dekisugi's close friendship with Shizuka, with whom Dekisugi shares a mutual affection and often spends time studying or engaging in leisure activities like reading and board games. His feelings for Shizuka are genuine, but his strong sense of integrity is demonstrated when he asks their friend Doraemon to reverse the effect of a gadget that artificially made Shizuka fall in love with him, stating he does not want to rely on a machine to win her heart. Unlike the main group of friends, Dekisugi rarely, if ever, relies on Doraemon's futuristic gadgets for personal gain. He usually interacts with them out of intellectual curiosity, but his problem-solving abilities are grounded in his own intelligence and hard work. In the franchise's feature-length adventures, he typically does not join the main cast on their journeys through time and space. Instead, he often appears at the beginning or in key interludes to provide scientific or historical explanations that help set the stage for the plot.

Looking ahead, Dekisugi’s future is clearly defined. He grows up to become an astronaut, a career that aligns with his childhood passion for astronomy, and is eventually stationed to work on a space project on Mars. He marries a woman who works with him on the space project, and they have a son named Hideo or Hideyo. In his adult years, despite having had feelings for Shizuka and once proposing to her, he accepts her decision to marry Nobita. He maintains a lasting friendship with the couple, even entrusting his son to their care while he and his wife are away working in space.