Original Name (Japanese): オー
Romaji Name: O
Nicknames: None
Series: Utsuro no Hako to Zero no Maria
Age: Unknown
Weight: Unknown
Height: Unknown
Date of Birth: Unknown
Blood Type: Unknown
Gender: Gender-neutral


O is a mysterious being introduced in the series “Utsuro no Hako to Zero no Maria”. O has no fixed appearance, instead taking on the image of everyone while resembling no one. O is also gender-neutral, being both male and female. Despite this, the majority of characters refer to O with male pronouns. O has been shown to be observant, impersonating certain characters in order to observe the protagonist, Hoshino, more closely.


O is revealed to be a creation of Maria’s desire. The name “O” is derived from the name of Maria’s older sister, Aya Otonashi. After her family died in an accident, Maria took on the burden and the dark sins herself.

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O has no fixed appearance, but takes on the form perceived by each individual. O has been observed to take the form of both human and non-human forms.


The extent of O’s abilities has not been fully explored, but it is known that O has the power to assume the appearance of others and observe them closely. O’s nature as a creation of Mary’s desire suggests that O may possess supernatural or otherworldly powers.


O’s origins are directly tied to Mary’s past and her family’s tragic demise. As the creation of Maria’s wish, O’s existence is deeply intertwined with the events and circumstances that led to the creation of this mysterious being.


Here are 6-8 FAQs about O from “Utsuro no Hako to Zero no Maria”:

Who is O?

O is a mysterious character who appears in the light novel series “Utsuro no Hako to Zero no Maria. O is an entity that exists outside the normal flow of time and space and is able to manipulate the world and people around it in ways that defy explanation.

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What are O’s powers?

O possesses a wide range of extraordinary abilities, including the power to manipulate causality, create closed time loops, erase people’s memories, and even rewrite the fundamental laws of reality. O’s true nature and the extent of her powers remain shrouded in mystery throughout the story.

What is O’s relationship to the main characters?

O’s interactions with the main characters, Kazuki Hoshino and Maria Otonashi, are central to the plot of the series. O often appears to manipulate events around the characters, sometimes helping them, sometimes hindering them, in pursuit of his own unknown agenda.

Is O a villain or an ally?

O’s motivations and morality are ambiguous throughout the story. While O’s actions often seem malevolent or cruel, he also occasionally helps the protagonists in ways that suggest a more complex agenda. The true nature of O’s intentions remains a mystery that is gradually unraveled as the series progresses.

What is the meaning of O’s name?

The significance of the letter “O” in O’s name is never explicitly explained, but it is speculated to represent the circular, cyclical nature of time and the infinite possibilities inherent in the universe that O is able to manipulate.

How does O fit into the overall narrative of the series?

O is a central and pivotal character in the “Utsuro no Hako to Zero no Maria” series, serving as a powerful force that drives the plot and challenges the characters’ understanding of reality. O’s role in the story is essential to exploring the series’ themes of free will, determinism, and the nature of existence.