It is unknown when exactly Yentsui was recruited into Cronos, but he is the seventh individual to be chosen by Hamilcar Barcas as a member of its leading council. Nothing is known about his activities before X-Day or which of Earth's provinces he governs following Cronos' takeover.
When Cronos Headquarters in Arizona is attacked by Zeus' Thunderbolt, Yentsui fights alongside Waferdanos and Dr. Barcas to protect the Sacred Treasure, a fossilized Ouranus ship that all of Cronos' advanced technology is based upon. When Gigantic Dark tries to steal the navigational spheres from the ship, Waferdanos attacks using his hair-drills while Yentsui transforms into his battle form, using his Zue Kong Zhan technique to produce interdimensional rifts around the battlefield. Although he and Waferdanos managed to injure the Gigantic Dark, the dark warrior ultimately tricked him into falling into his own trap - he was pushed through one of his own portals, straight into the waiting hair-drills of Waferdanos, which skewered him. The shock caused him to collapse his portals, and unfortunately he was only halfway through at the time. He managed to hang on for a few more minutes, thanks to the bio-energy from his zoacrsytal, and saved Dr.Barcas' life by creating a portal to the outside; surrendering his zoacrystal back to him, his final act in life was to mock the Guyver, as he was trapped in a base that would explode in seconds. He did not see how the Guyver and his companion Griselda used his one remaining portal to flee after Barcas.