Ryu is the former Junior Welterweight Boxing Champion of Japan. Known for his successive winning streak, he was framed for murder by greedy boxing promoters in Las Vegas after refusing to rig a championship fight. He was intercepted by Joker while being extradited to Japan for prosecution. Joker offered him a choice: work for ISSIS as part of J.A.K.Q., or serve his prison sentence. Higashi reluctantly accepted.

A rough, gruff, and headstrong individual, Higashi is a bit of a loner who prefers to work solo, though he keeps in touch with his former boxing peers. He is fond of fast cars and jazz music. His bionic enhancements allow him to generate and manipulate immense electric currents.

From his right index finger, he can deploy his Eleki Cutter to slice through dense objects, and from his left ring finger, he can fire the Dia Laser to shear through metal. As Dia Jack, Higashi wields the powerful Dia Sword, which he imbues with electrical energy to slash through solid steel or fire lethal bolts of lightning at Crime cyborgs.