Deletloss, a mysterious and destructive computer virus, emerged within the Magical Gate—a global cyber park housing children's uploaded consciousness. It initiated its assault by corrupting and brainwashing the Web Knights, protective programs turned against their charges. Gladion alone evaded corruption.

Before surfacing in Earth's networks, Deletloss invaded Couria in the Andromeda Nebula, 2.4 million light years distant, annihilating the planet. Gladion, then a Courian warrior, confronted the virus in mutual destruction: Gladion shed his physical form to become data, while Deletloss persisted as residual data despite apparent defeat.

Resurrected within Earth's systems, Deletloss continued corrupting and destroying. It later generated Dark Gladion, a corrupted counterpart that battled Gladion and Kento Yuki. During their final clash in Couria’s ruins, Deletloss nearly erased Gladion entirely until Kento web-dived into Gladion’s spiritual world, restoring his memory and reviving him.

The conflict culminated on Couria as Gladion and Kento fused into an angelic cyber datanoid. Deletloss succumbed in this encounter but survived the subsequent explosion.