"Flower, Sun, and Rain" shares its setting and some characters with some of Suda's other games, such as "Moonlight Syndrome" and "The Silver Case". Despite acting as a sequel to "The Silver Case", and featuring a version of that game's protagonist Sumio Kodai, the story does not present itself as initially related to "The Silver Case". This approach was inspired by the Star System utilized by manga artist Osamu Tezuka in which the same characters appear in different works with different roles. The opening scene, where Mondo drives his car towards the island, was put into the game to both introduce Mondo's character to newcomers, and to throw players of "The Silver Case" off guard by the familiar name "Sumio" contrasting with Mondo's the unfamiliar personality. It also helped establish the setting and get the player used to Mondo's point of view. His portable computer Catherine, stored in a suitcase, is said by Suda to contain the events of "The Silver Case" within it. Despite this, it literally being a "silver case" was coincidental rather than a deliberate reference to the previous game's title.