Eiichi Kite, universally nicknamed Kiteretsu, is an 11-year-old fifth-grader living in Tokyo. He wears square glasses and sports signature attire: a red-yellow visor, light blue T-shirt, dark blue pants, and green shoes. Possessing exceptional intellect in mechanics and invention, Kiteretsu struggles significantly in athletics. He maintains solid academic performance without failing, though his intense focus on inventing gadgets sometimes impacts his school results. Financial limitations constrain his inventive work; he funds projects solely through allowances and New Year's money, leaving broken inventions unrepaired until savings permit. His personality merges analytical thinking and logical problem-solving with genuine care for close relationships, counterbalanced by tendencies toward social detachment and anxiety when his independence feels challenged. These traits align with INTP personality types and Enneagram Type 5 (The Observer), reflecting his knowledge-seeking drive and self-sufficiency.

Kiteretsu's character is profoundly shaped by his ancestry as a descendant of Edo-period inventor Kiteretsu Saisama. Saisama's encyclopedia provides foundational knowledge for his inventions, a connection reinforced through dream interactions with his ancestor. At home, his mother Michiko enforces strict academic expectations, compelling Kiteretsu to hide his inventing, while his father Eitaro actively supports his creativity. Both parental relationships feature mutual affection despite differing approaches. Future timelines confirm Kiteretsu marries childhood friend Miyoko Nonohana; they have a son named Eitaro, honoring Kiteretsu's father.

Kiteretsu's primary mechanical companion is Korosuke, a samurai-inspired robot assistant he built using the ancestral encyclopedia. Korosuke speaks with distinctive linguistic patterns ending sentences in "nari" and possesses variable size-changing capabilities. Their bond extends beyond inventor-creation into deep friendship, though Korosuke's occasional naivety leads to comedic or problematic situations during adventures. Kiteretsu's social circle includes Miyoko Nonohana, portrayed as his intellectual equal and future spouse; Kaoru Kumada (Butagorira), a vegetable-loving bully whose role shifts toward comic relief; and Kōji Tongari, a wealthy but easily frightened peer often targeted by Kumada. This group dynamic echoes other Fujiko Fujio ensembles. University student Benzo Karino serves as a mentor figure, offering guidance during their exploits.

Kiteretsu's inventions, primarily derived from his ancestor's encyclopedia, include numerous gadgets. The most notable is a time machine facilitating journeys mainly to historical periods, with rare future travel as an exception. Other documented inventions encompass a Small Light and Magic Umbrella, though practical limitations persist, like the time machine's general restriction to past destinations. His cross-franchise connection to Nobita Nobi (Doraemon) manifests as a familial cousin relationship in specific regional adaptations; their narratives intersect in media such as the crossover special "Doraemon and Kiteretsu Daihyakka: Korosuke's First Approach".