|This article is about a/an ally in Kamen Rider Decade.|
- For the Original Character from Kamen Rider Ryuki, see Reiko Momoi (Ryuki).
Reiko Momoi (桃井 玲子 Momoi Reiko) is the editor of the Atashi Journal. When Natsumi finds her upon arriving in the World of Ryuki, Reiko mysteriously dies, leaving Natsumi as the sole suspect of her murder. However, Ryuki uses the Time Vent Card to alter time and save her, while simultaneously revealing the true murderer.