Zero Sr.
Zero Sr.
Aliases Zero
Sigma Klim
Zero-Bosu ("Zero Boss") *
Gender Male
Age 67 (born c. 2006)
Status Alive
Hair color Gray
Eye color Unknown
Relatives Unknown
Occupation Scientist and doctor
Appearances Virtue's Last Reward
Zero Time Dilemma (as Sigma)
Voice Akio Ōtsuka (Japanese)
Jamieson Price (English)
This article describes Zero Sr.'s identity as he is referred to by the players of the Nonary Game: Ambidex Edition. For his true identity, click here.
"We trudge through our lives with no greater understanding of our ultimate goal. You might say we don't understand what we're building. Only an intelligence of a higher order than ours can understand what we're doing. Imagine how we might look to such an intelligence."

Zero Sr. is the orchestrator of the Nonary Game: Ambidex Edition, and the mastermind behind the events of Zero Escape: Virtue's Last Reward. The players dubbed him "Zero Sr." to distinguish him from "Zero Jr.", the AI acting on Zero Sr.'s behalf.


Sigma reflection

Zero Sr.'s face in a reflection.

Zero is an elderly man with gray shoulder-length hair.

He wears a formal black jacket over a white shirt, a pair of jeans, and gray boots. His right eye is covered by some sort of bionic lens since he lost it decades prior, and his right hand is covered by a glove. His left hand has a bracelet on it.

Zero is only seen once by Sigma, Tenmyouji, and Quark in Tenmyouji END, as a hologram, and by ? in Another Time END.


Zero is actually the 67 year old version of Sigma.

As seen in Zero Time Dilemma, on December 31, 2028, Sigma lost both his arms (which were replaced by mechanical prosthetics), and his right eye in trying to save Diana and Q team from the Underground Shelter in Nevada. He escaped the shelter with Diana and Phi.

After the mission, which ultimately failed, causing Radical-6 to spread across the world, Sigma went to the Moon and spent the next 45 years working on the AB Project, which would be the key to stopping the spread of the disease with the help of the consciousness of his younger self.


Zero Sr. with Akane in K's flashback.

During those 45 years, Sigma would meet Akane Kurashiki, who would help him with the project, and become part of Crash Keys. He would also create Artificial Biological Tissue (ABT) and the GAULEMs, including Luna, who would participate in the AB Project. He also produced his clone and "spare", Kyle Klim, and the AI Lagomorph, along with the bracelets and Chromatic Doors, as well as asking Tenmyouji and Quark to come to Rhizome 9 under the guise of seeing Akane.

Virtue's Last Reward

After fully developing the AB Project, Sigma's consciousness switched places with that of his 22-year old self. While the younger Sigma participated in the Nonary Game in 2074, the older Sigma would infiltrate the trap-infested facility where Radical-6 was first noticed in 2028 with the help of Phi, where he would lose his arms and eye.

Four months later, in April 2029, his consciousness would switch back with his younger self's, who had reached the end of the game, where his younger self would begin research on the project, thus completing the cycle.

Tenmyouji END

Sigma finds a hologram of Zero Sr. in the Director's Office while searching for Tenmyouji and Quark prior to the third round of the AB Game.

In his message to Sigma, Zero Sr. mentions termites, how a termite mound is similar to a rhizome, and likens humanity to termites. He says that mankind might be building something in unison they are not aware of and can only be appreciated by the intelligence of a higher order. Every human is an "oblivious cog in a tremendous machine programmed by millions of years of human DNA." The concept is that the termites all do their work, fill their niche, and mind their own business. Their activities by themselves are mundane. However, when humans look on a termite mound, they see a wonder, a work of art that is a product of the collective efforts of the termites. If one could look at human activities from a more all-seeing vantage point, perhaps the activities of humans would be equally magnificent.


Zero Sr. giving the password of Bomb #1 to Sigma.

He then gives Sigma the password for Bomb 1 (BQZ RGJ DXR). He asks Sigma if he is aware of his time jumping abilities and warns him not to tell anyone about their meeting, otherwise he will penalize him. Before the message ends, Zero Sr. says that he looks forward to speaking with him in person.

Before Sigma saw the hologram, Tenmyouji and Quark already saw it before Sigma did (this is revealed in question 74 in the VLR answers). When Tenmyouji and Quark returned to the office to get Akane's picture which they accidentally forget, they saw the hologram, which leads them to betray Sigma as they realized that Sigma was Zero Sr., due to Sigma actually being and looking 67 years old, something he was unaware of.

Phi END and Another Time END

Before "Kyle" wakes up, Zero Sr. instructs Phi that she can answer any questions about the test site to anyone besides "Kyle". He also carries "Kyle" to the infirmary where he and Dio are looked after by Luna. After he wakes up, ? sees a hologram of Zero Sr. after speaking with Phi. He states that he cannot answer any questions about the Mars Mission Test Site to ? because if he did, the timeline where the virus was contained would disappear.

Zero Time Dilemma


Zero Sr. in Zero Time Dilemma.

See also: Sigma Klim#Zero Time Dilemma

Zero Sr.'s consciousness inhabits the body of Sigma in Zero Time Dilemma in order to save the world from Radical-6, alongside Phi.

Sigma survives in the True Ending of the game. His fate after the events of the Decision Game in this ending is unknown, including if Sigma's older consciousness remained in this version of him. It could also be theorized that instead of a consciousness swap, his memories of the events of Zero Time Dilemma and Virtue's Last Reward have all been merged into a single consciousness, with all his memories intact.


  • "You undoubtedly have as many questions for me as there are stars in the sky. As you can see, however, this is only a recording. I will therefore be unable to directly answer any questions. Ask if you wish, but I cannot respond. Now, where to begin... There are many things I wish to tell you... But unfortunately our time is limited. As such the information I can provide is also limited."
  • "First, I will tell you about termites. Hm. In retrospect, I suppose that's a rather odd thing to say. I imagine you look rather bewildered right now. Perfectly understandable. The person who kidnapped you and threatened you with death is lecturing you about insects. I suspect it hardly seems fair."
  • "Each termite is simply an oblivious cog in a tremendous machine programmed by millions of years of termite DNA. It is doubtful an individual termite has any idea what its contributions are helping to create. But a human does. We can appreciate the elegant forms of their alien cathedrals... We can see the simply beauty of their perfect functionality... We can understand the splendid planning of their structure... In other words, only an intelligence of a higher order can understand the beauty of what a termite builds."
  • "Now consider humans. Why are we alive? Why do we love, and give birth? Why do we create? From where do our cultures spring? There are many theories, but no one knows the truth. We are oblivious cogs in a tremendous machine programmed by millions of years of human DNA."
  • "We trudge through our lives with no greater understanding of our ultimate goal. You might say we don't understand what we're building. Only an intelligence of a higher order than ours can understand what we're doing. Imagine how we might look to such an intelligence. We may be building some structure so perfect and elegant we can't even perceive it. Whatever it is, we've likely been building it on a dimension just above the ones we know since time immemorial. If we are like the termites, then what we've been building is almost certainly something of tremendous beauty. And you are about to catch a glimpse of it. Or have you already...?"


  • While Sigma and Phi are discussing the Prisoner's Dilemma and the AB Game during the Cyan door route (the Phi & Sigma VS Alice match-up), Phi tells a made-up story (as an analogy to the AB Game) about a detective arresting two characters named "Apple" and "Banana". Jamieson Price, Zero Sr.'s actor, voices the detective.
  • It is possible that Zero's speech about a "higher power observing humans" was actually a subtle instance of breaking the fourth wall, and that his speech was nodding to the players of the game observing the fictional world of the series.