|This article is about a/an character in Kamen Rider Ryuki.|
|Series:||Kamen Rider Ryuki|
|Ally Type:||Senior Reporter (ORE Journal)|
|First Appearance:||The Secret Story's Birth|
|Last Appearance:||A New Life|
- For the Character from Kamen Rider Decade's World of Ryuki, see Reiko Momoi (Decade).
Reiko Momoi (桃井 令子 Momoi Reiko) is a no-nonsense reporter whose goal is to uncover the truth behind the disappearances that are inextricably linked to the Rider War. She also became Kitaoka's target for unwanted affections.
Reiko was a reporter for ORE Journal and was researching about the sudden unexplained chain of disappearance, which led to multiple confrontations with the authorities. In the heat of her investigation, their Chief Editor assigned their new member (Shinji) to be her assistant so that he could learn from her. After some mishaps, she instructed him to find connections between the missing persons in their office's computer and left to take care of another appointment. While investigating an apartment of one of the recent victims, she was tagged by the monster that abducted the resident of that room. She was about to be attacked when her cellphone rang and went to fetch Shinji, who ditched his assignment and investigated on his own. Unknown to her, the monster followed her and was about to abduct her when he noticed a Rider, allowing her vehicle to escape the webbing.
The next day, Reiko berated Shinji again when the latter tried to talk her out of the investigation out of concern. She thought Shinji meant that she's only trying to get a big scoop.
Heading out to investigate another missing persons incident, she was expecting Shinji to assist her investigation, not knowing that he was fighting the cause of the disappearances. Back at the office, she asked him where he was at that time, in which he only said that he has a different way of investigating things.
One of her investigations led her to an elementary school where Zelles monsters who attack in groups abducted a teacher. She was surprised to see Shinji there as well, supposedly investigating the attacks on children.