Ai Nonomura is one of the main characters in the anime series Popotan. She is the eldest of the three sisters traveling through time in their mysterious house. Ai is responsible, caring, and often acts as the mother figure to her younger sisters, Mai and Mii. Throughout the series, she searches for answers about their journey and the meaning of the mysterious word 'Popotan.' Ai's role is central to the emotional and narrative development of the story.