Ren works as a researcher at Vermilion City's Cerise Laboratory under Professor Cerise. He sports messy yellow hair, fair skin, and a standard lab outfit: a white coat over a yellow Magnemite-print t-shirt, red pants, and gray shoes with blue stripes.

His personality blends intellectual skill with pronounced timidity. Ren possesses expertise in Pokémon biology, readily explaining complex topics like Dratini evolution or Pokémon Egg care. However, he remains visibly frightened by paranormal phenomena, a fear rooted in ghost-related rumors encountered as Professor Cerise's student alongside his friend Laxton. This phobia makes him a regular target for Ash's Gengar. Ren sometimes arrives late to work and can struggle with social cues, occasionally offering overly intricate explanations about Pokémon evolution to colleagues.

His primary partner is a Magnemite named Francois, used for both research and practical tasks like jumpstarting electronics. Francois exhibits selective eating habits, consuming only electricity from antique appliances. Their bond began when Ren found the Magnemite at a café, inspiring its nickname. Ren displays fierce dedication to Francois's safety, confronting personal fears such as heights to protect it.

His background beyond his academic role is largely unexplored. He holds deep respect for Professor Cerise and collaborates with fellow assistant Chrysa. Ren interacts with research fellows Ash and Goh, notably assisting Goh with academic studies. His development includes facing his phobias when necessary, particularly during incidents involving Francois.