Takeshi, usually known by the nickname "Gian" (ジャイアン, Jaian) from English word "giant", is the big, strong, and quick-tempered local bully. He is known for his confidence in his terrible singing voice, though he considers himself a great singer. He regularly subjects the neighborhood children to horrendous singing recitals, which is sometimes combined with his equally bad homemade dinner and his atrocious fashion sense. He also frequently steals other children's toys and books under the pretext of "borrowing" them, unless the toy is damaged. This is how most fans considered Gian to be the antagonist of this show. However, he does not hesitate to help Nobita and his friends when they are in real trouble, which often occurs in the movies.

Several of the stories revolve around Nobita and his friends' efforts to avoid Gian's concerts, and several chapters summarize his friends efforts to avoid visiting Gian's house on his birthday because of his selfish nature. After reflecting on one event about his birthday, Gian thought of himself why he wasn't popular among his peers. After getting a lecture from Doraemon to see what an unruly character he is, Gian realize that he should have been a better person and he begs Doraemon to give him another chance. However, things didn't go exactly as planned when his friends at school or at the streets mock him to see how weird Gian was acting and get kicked by Suneo after learning his attempt to become gentle to his peers. This led him to lose control of his temper and start attacking his friends again.

Although he bullies the other children (mostly Nobita), he is terrified of his mother, who runs the local grocery store, a fact Nobita and Doraemon sometimes use in their favor. He founded his own baseball team named after himself. Although Nobita is often blamed for the losses against the baseball team's rival, the "Tyranos", Gian and Suneo still force Nobita to play because they do not have enough players.

Gian also has a younger sister named Jaiko, whom he adores.