Len/Lex, known in the original Japanese version as Ren Hiyama, is a supporting character in the first season of the anime LBX: Little Battlers eXperience. His background is that of a calm, unassuming coffee shop owner who runs a café called Blue Cats. However, he is also a member of the covert organization known as Seeker and is recognized as a legendary LBX player under the alias Lex. Len/Lex pilots a customized LBX called G.Rex, a modified Salamander-type unit that is slightly larger than the standard model, reflecting his personal specifications.

In terms of personality, Len/Lex initially presents himself as a friendly and composed individual, but his motivations are driven by a deep desire for personal vengeance. He secretly takes the plans of the Innovator, a group that seeks to control LBX technology, and adapts them for his own ends. His primary role in the story is that of an antagonist revealed in the second half of the season, where he masterminds the creation of an android version of Yoshimitsu Kaidou as part of his scheme. He manipulates events from behind the scenes, using his influence within Seeker to advance his agenda.

Len/Lex’s key relationships include his interactions with the protagonist Ban Yamano and his friends, whom he initially aids before his true nature is exposed. He also has ties to the Innovator and to the larger LBX community through his legendary status. Throughout the series, his character develops from a mysterious ally to a central adversary, ultimately facing the consequences of his actions. Notable abilities include his exceptional skill as an LBX pilot, which earned him the title of legend, and his proficiency in strategic planning and technological manipulation. His G.Rex unit is equipped with enhanced performance capabilities, making him a formidable opponent.