Rex Taromaru, who operates under the alias T.Rex, is the assistant photographer and third member of the group Secret Aliens. Abandoned at birth at the foot of a Tyrannosaurus Rex fossil in a museum, he was raised in an orphanage where his youth was defined by delinquent behavior.

His path changed when Tom confronted him with a Hypnosis Microphone to prevent him from a life of crime. After a decisive defeat, Rex was swayed by Tom's offer to "see the world together," leading him to accept the position as Tom's assistant.

Rex exhibits an impatient and hot-tempered nature, yet he demonstrates a serious and dedicated professionalism in his work. He has a tanned complexion and ear-length purple hair. His eyes have been noted as blue, green, or turquoise. His appearance is distinguished by an ahoge, multiple ear piercings, a frequent choice of tank tops, a necklace, and several visible tattoos.