Omi Jin is a fifteen-year-old boy who takes part in the survival game at the center of Tasuketsu: Fate of the Majority. He is Japanese, with purple eyes and short purple hair, and he is notably small even for his age, standing only 134 centimeters and weighing about 32 kilograms. His birthday falls on March 20 and his blood type is AB. His small stature, distinct appearance, and unusual way of speaking make him stand out from everyone around him.

His past is marked by hardship and loss. As a child, he was subjected to secret experiments conducted in a facility, and he lost his parents along the way. He was one of the survivors of those experiments, and that experience is connected to him gaining a powerful special ability known as the Veto Right, one of the mysterious abilities called Privileges that certain participants wield in the game. Because of this ability and the sharp, strategic mind he is known for, he is an indispensable figure among the other players, often filling the role of a strategist rather than a direct combatant.

Omi Jin is defined by his unique dialect and his quick, analytical thinking. His difficult background appears to drive him to actively use the privilege he holds; instead of remaining a passive victim of the circumstances that shaped him, he employs his Veto Right in an effort to change the course of events in the story. In that role, he works alongside the other boys and girls who possess Privileges as they confront the Emperor, the powerful mastermind behind the game. His development lies in how he carries the weight of his traumatic past while holding a privilege as significant as the Veto Right, growing into a participant who can meaningfully influence the fate of the majority rather than merely enduring it.