The character in question is Ikuko, not Ikkuko. Ikuko is the young niece of Kyoko Otonashi by marriage, being the daughter of Soichiro Otonashi's sister. She is a rambunctious and spirited elementary school girl when she is first introduced, and as the story progresses over several years, she matures into a young woman on the verge of starting college. Her presence serves as a significant link between Kyoko and her deceased husband's family, the Otonashis, who are portrayed as a kind and supportive counterpoint to Kyoko's own relatives. It is her grandfather, Mr. Otonashi, who owns the Maison Ikkoku boarding house, and he plays a quiet but crucial role in the lives of its residents.

Ikuko’s primary role in the narrative is to create an opportunity for Yusaku Godai to demonstrate his maturity and sense of responsibility. During a visit to Maison Ikkoku, she quickly becomes fond of Godai and insists that he become her private tutor to help her prepare for middle school entrance exams. While Ikuko seems more interested in goofing off and gossiping about Godai's love life than in serious studying, this tutoring job becomes Godai's first steady source of income. More importantly, it provides him with a legitimate reason to interact with Kyoko in a responsible capacity, offering him a chance to prove his reliability to her and to grow closer to the Otonashi family. Kyoko, ever watchful, tends to hover during these tutoring sessions, partly out of a genuine concern that Godai’s lazy habits might rub off on Ikuko, though it is often Ikuko herself who steers the conversation away from her lessons.

Although her appearances are not as frequent as those of the main tenants of Ikkoku, Ikuko represents the warmth and acceptance of the Otonashi family, who consider Kyoko their own and continue to love her unconditionally after Soichiro's death. Her energy and fondness for Godai also create a lighthearted contrast to the more chaotic meddling of characters like Mrs. Ichinose and Yotsuya. She does not possess any notable abilities beyond the typical energy and cleverness of a young girl, but her growth from a child to a young adult is one of the subtle markers of time passing throughout the long-running story. Her relationship with Kentaro Ichinose, the young son of another tenant, begins after they spend a day together at the beach, leading to him developing a quiet crush on her of which she remains largely unaware.