Introduced in the second episode of the Ami-centered episodes, Ryuji Kouno is university student and notorious playboy that Ami Nonomura meets at a disco club where they share a dance together. Not wanting to let her go back home drunk, he takes her to his apartment and the two have a one-night-stand together. Intrigued by how experienced she was in bed during their sexual encounter, Kouno desires to have Ami again and takes her back to his place and pressures her into having sex with him again. Kouno's rival for Ami's affections is her beloved brother, Hiroshi. From then on during the course of the Ami episodes of the Cream Lemon franchise, Kouno and Ami do become lovers.

In the "Ami, From Then On" chapter of the series, he has become a company president for a music production firm and is managing aspects of Ami's career. He is still a playboy however and has an affair with his secretary. Kouno asks Ami to marry him and he finally meets her brother, Hiroshi for the first time.