Guido is a young war orphan who resides on the remote island that becomes the central setting of the story. He is among a group of children whose lives were shattered by the violence of the One Year War, having lost their families to the conflict. The former Zeon soldier Cucuruz Doan, burdened by guilt after accidentally causing the deaths of civilians and then being ordered to kill the surviving children, instead deserted his post and took them to the island, where he swore to protect them.

As a member of this makeshift family, Guido lives alongside several other children, including Amado, to whom he is the younger brother. He holds a specific and important role within the small community’s daily life, being the one put in charge of fishing. This duty highlights the group's need to be self-sufficient and contribute to their collective survival, separate from the war that rages beyond their shores. While the story primarily focuses on the moral burdens of the adult characters like Doan and Amuro Ray, children like Guido serve as the living embodiment of what the war has destroyed. They are the reason Doan has rejected violence and chosen a life of quiet atonement, representing the innocent future he believes is worth protecting at all costs. Guido's existence on the island is defined by this new, fragile peace, and his role as a provider through fishing underscores the community’s ongoing efforts to maintain a semblance of normal life. He does not display any notable combat or piloting abilities, as his world revolves around survival and the safety provided by his guardian.