"12,800,000 meters. One second."
— Why-man using Senku's voice to petrify the planet, Dr. Stone, Chapter 191
Why-man (ホワイマン Howaiman) is the name Ryusui gives to the source of powerful radio wave messages the Kingdom of Science receives after putting a large radio transmitter into service. The name is chosen as the messages consisted only of the word "why" in Morse code when the signal was first heard. Determining the nature of Why-man is a major goal of the Source of the Petrification Saga.
Why-man is the main antagonist of Dr. Stone.
The face and gender of Why-man is unknown, but is normally shown in the manga as an extremely gaunt, skull-like face with hollow eye sockets and no nose. They've also got two layers of teeth, with the outer/top layer looking similar to a child's teeth x-ray.
The true nature and motives of Why-man are currently unknown. However, their main goal seems to be to keep humanity petrified, as both with Treasure Island later on the Perseus, Why-man attempted to petrify everyone using the Medusa.
Gen noted, analyzing Why-man's behavior, that it must be an entity with a will of it's own, and considers itself far superior to the Kingdom of Science, such as to completely disregard their attempts at communication, but also not retaliating with full force.
Why-man is first heard communicating with the Kingdom of Science using Morse code on the motorboat, soon after the "crazy-strong" radio tower is turned on for the first time. The message that saturated the radio frequency the Kingdom was using consisted of one word being repeated over and over: "Why?".
This call shocks the members on the boat, with Chrome telling Why-man to stop shouting, despite his friends telling him to pipe down. Senku responds to the shouting via their radio by calling them out as the source of the petrification. The signal immediately stops, leaving the group to speculate on who or what the signal came from. The group chose to assume Why-man is an enemy, as the worst that can happen is they over-prepare for someone who is in fact an ally.
During the voyage to Treasure Island, Soyuz comes forward as a previous inhabitant of the island. Chrome speculates that Why-man may be a member of the Treasure Island tribe, as there can't be many other living humans in existence thanks to the petrification.
After the conflict on Treasure Island is done and the cellphone is fixed, Ruri tells the team that they've been receiving a strange message. Their connection is then cut off by a second strong signal that takes over the radio waves in an attempt to activate the petrification device remotely, with the stated distance being Earth's diameter (12,800,000 meters) and the time as 1 second. This call has the Kingdom of Science confirm that Why-man was an enemy who wants to see all of humanity petrified. However, the voice, as noted by Ukyo, is a synthetic voice matching Senku's.
The source of Why-man's transmissions is apparently on the Moon.
Dr. Xeno reveals that he is also aware of Why-man and the signal coming from the moon, which surprises everyone. Despite their enmity, he proposes an alliance to defeat Why-man with Senku who gets excited as Xeno hopes that they can work together to figure out the source of the Petrification and they proceed to exchange information.
Following the fall of the Science Kingdom personnel stationed in Corn City, Joel exploits Why-man's regular interval radio to petrify everyone, including Senku, by using his modified watch that also serves as radio transmitter.
Seven years later, a revived Senku decides it is time to confront Why-Man before another calamity unfolds. To that end, Senku revives Xeno who agrees to put aside his enmity with them to defeat a common foe. He agrees to construct a rocket for them.
Following the revival of his followers, Xeno informs them about Why-man and status on the moon. The Americans were stunned someone was actually on the moon and by the thought of space travel in the Stone World.
On the way to Europe, Why-man sends a message to the Kingdom of Science, with Chrome, Ukyo, and Leonard who were stationed at the communication devices receive. Why-man's message is translated as asking "DO YOU WANNA DIE?", shocking everyone. When Gen suggests a response which Francois delivers, but Why-man's messages stop without a response. Senku speculates Why-man is likely desperate but not so to rain down more Petrification Weapons and decides that with limited time they must prepare for space travel.
Following the revival of the American colony the Kingdom Of Science inform Dr. Brody and his followers about Why-man.
- Ryusui believes Why-man petrified themselves if they truly caused the first Petrification event. If that is the case it is unknown how they were able to revive themselves.
- It is unknown if Why-man is directly connected to the petrification weapons that fell on Treasure Island.
- Why-man's desire to petrify the world a second time ironically may have turned against him as Senku used the signal to save his dying allies.
- It is unknown how Why-man knows of Senku.
- It's possible Why-Man is a misanthrope who loves the environment; which would explain it's attempts to keep humanity either petrified or primitive like the Post-Petrification humans, so they can damage the planet again.