Eisai Dekigusu, also known as Hidetoshi Dekisugi, is a highly intelligent and well-regarded classmate of Nobita Nobi. He consistently achieves perfect exam scores and excels in athletic pursuits like baseball, soccer, and track. His talents further encompass artistic skills such as realistic painting and cooking, alongside sleight-of-hand magic. Dekisugi maintains a modest, gentlemanly demeanor, never boasting about his abilities and often encouraging others. His personality emphasizes reasoning, rationality, and a scientific approach, showing only measured curiosity toward extraordinary gadgets.

Dekisugi maintains a friendship with Shizuka Minamoto, frequently engaging in academic or casual activities like homework, board games, outdoor painting, and cooking. In adulthood, he proposed marriage to Shizuka, but she declined, feeling he would not require her support. His dynamic with Nobita Nobi is complex; Nobita often displays jealousy over Dekisugi's academic and athletic superiority and closeness to Shizuka, sometimes damaging Dekisugi's belongings or attempting to undermine him with gadgets. Despite this, Dekisugi consistently treats Nobita as a friend, defending him from bullies and discreetly helping Shizuka bake a birthday cake for him. Dekisugi also demonstrates forgiveness, such as offering to tutor the envious Gariben after discovering Gariben's attempts to sabotage his academic performance.

In the future, Dekisugi becomes an astronaut, marries, and has a son named Hideyo. He appears as an adult guest during the events surrounding Nobita's wedding in Stand By Me Doraemon 2, where his earlier proposal to Shizuka and her rejection form part of his background narrative. His name, "Hidetoshi Dekisugi," carries meanings reflecting his capabilities: "Hidetoshi" translates to "unusual talent," while "Dekisugi" derives from "dekisugiru," meaning "over-achieving." Alternate readings and international adaptations exist, such as "Ace Goody" in the American English dub.