Toshi Igarashi is a Japanese high school student distinguished by his black hair and blue eyes. As the younger brother of Nachi Igarashi, his life takes an unexpected turn following the arrival of extradimensional Domni-Matrixes on Earth. He forges a romantic relationship with Assembler, one of the entities initially dispatched to conquer humanity. This profound connection compels Assembler to abandon her original mission alongside Compiler, choosing instead peaceful coexistence with Toshi and Nachi.

Toshi possesses no combat abilities or superhuman traits, functioning solely as an ordinary human. His narrative significance stems entirely from his personal bond with Assembler, where their romance acts as the catalyst for her defection from the cyberspace council's objectives. The story delves into their relationship dynamics, particularly within the second OVA episode, which centers on their interactions devoid of significant action sequences.