Sōichirō William Mori stands among the eight primary characters within the core narrative. His Japanese name, written as "森 ウィリアム 聡一郎," positions "Mori" as his surname. Identified by his vibrant multicolored hair and striking mint green eyes—consistent in all depictions—he also bears a distinguishing birthmark or mole. A Japanese teenager nicknamed "Bill," he hails from a wealthy background. As an active member of the central friend group, he regularly engages in surfing activities alongside them. This character maintains his role identically across both the original film trilogy and the subsequent television series adaptation.