Riyu Momose (百瀬リユ Momose Riyu?) is a main character and a female protagonist in Akiba's Beat. She is a 14 year-old girl and a popular Japanese idol who resides in Akihabara as one of its poster girls, as well as often holding a mini live handshake meeting which led to her experiencing the "eroded delusion". She has a love for rabbits and cherry blossoms. She later becomes close friends with Kotomi and Saki. She is known for her nickname "Mippyon" ("Rippyon" in the Japanese version) by fans.
She carries the title, "The Ever-Smiling Idol" (笑顔満天なハッピーアイドル?).