|This article is about a/an ally in Kamen Rider Den-O.|
Airi Nogami (野上 愛理 Nogami Airi) is Ryotaro's elder sister and owner of the Milk Dipper that belonged to their parents. A motherly figure to her brother, she constantly tries to help Ryotaro in an attempt to find his lucky star. Originally, she was to be married to Yuto Sakurai on January 10, 2007, pregnant with their unborn child who is the Junction Point. However, Kai's intent to kill them to destroy the Junction Point forced Airi to allow Sakurai to erase himself and their child from normal time so they can evade Kai and his Imagin army. This resulted with Airi losing all memory of her fiancé Sakurai. Although she actually goes to the place she and Sakurai spent time together, the park at Kibōgahara after being hypnotized by Miura on accident, she cannot remember much, particularly about the railway watch which is all that Sakurai left.
When she encounters Fujishiro and is kidnapped, Airi begins to clearly remember Sakurai until Yuto uses his final Zeronos Card, wiping her memories of his future self as a result. However, Airi feels that something is missing with Ryotaro hoping it means she is regaining her memory. When Yuto later uses the red sided Zeronos Card, all of his memories with Airi are burned when he assumes Zero Form for the first time. But eventually, when Ryotaro meets Airi's past self, she is revealed to have known about Sakurai obtaining the ZeroLiner and the identity of the Junction Point: their daughter Hana.
In the series finale, Airi regains her memories of Sakurai as they meet one final time before he fades from existence, though she is confident that they will meet again in the near future. During Climax Deka, Airi meets Ryutaros face to face, giving him a treat which he bashfully takes. Later, during the events of Episode Red: Zero no Star Twinkle, Airi meets with Yuto and now knows that he is her lover's past self. Though she believes that their future can no longer be with Yuto as he is, she realizes that she may be wrong after he saves her and shows her the nighttime sky on their way home.