Ten years before the start of the game, Yomiel was a top systems engineer and, according to him, one of the best in the industry. He was selected to help work on a new way to organize the nation's national secrets, for which he worked to built the core of the system. Due to the value of the project, it began to be infiltrated with spies from many organizations around the world. Yomiel was suspected to be one such spy, and was arrested. He was later interrogated by Cabanela, who pushed him too hard and drove him to fear and hopelessness. Cabanela left the interrogation room at some point, forgetting his gun. Yomiel used this gun to escape and ran off to Temsik Park with Jowd in hot pursuit. Here he found a younger Lynne and took her hostage out of desperation.
Right before Jowd was going to shoot him, the Temsik meteor happened to fall from the sky, a fragment of it piercing Yomiel in the heart, instantly killing him. The meteor had mysterious, alien powers that gave Yomiel's ghost the ability to perform ghost tricks, mainly the ability to manipulate small living creatures, as well as turned his body invincible with its time-stopping powers.
Yomiel initially lost his memories after his death and transferred his soul to a black kitten that was wandering in the park. After regaining his memories, he used his powers to possess his own dead body in the morgue to see his fiancee Sissel, but she had committed suicide just before he reached her, leaving him only a note that said "I'm coming to you, Yomiel."
For ten years, Yomiel wandered the world, but nobody noticed a lonely dead man. The only friend he had was the black kitten, who he named Sissel after his fiancee. Eventually, his powers developed enough that he obtained the ability to control people both alive and dead. Yomiel's mind became twisted, and that is when he decided to get revenge on everyone else who killed him.
He contacted Sith, and they made a deal which would not only give Yomiel his revenge, it would also give him a new life where he would be able to live normally, grow old and die in exchange for the meteorite fragment in his heart that killed him.
Yomiel first took revenge on Jowd, by killing his wife Alma by manipulating his daughter Kamila into altering the birthday contraption she had made for her by adding an antique gun to it, and framing Kamila for it.
Right before the events of the game, he met up with Lynne at a junkyard, and told her that he was the one who took her hostage. He then takes control of Lynne, and tries to shoot his own body in order to have Lynne framed for murder by the junkyard cameras. Unfortunately for him, Lynne was able to partially resist his takeover and made him miss the first shot, and accidentally hit the cat carrier Yomiel was holding, killing Sissel inside it. The second shot hits and "kills" Yomiel. Yomiel then escapes by possessing his cat, only to realise that Sissel is dead. Nevertheless, he runs from the scene with Sissel's corpse, leaving his own body behind, knocking it to the lower level of the junkyard in the process.
The plan was for him to collect his body from a fake doctor planted at the crime scene, but Cabanela found out the fake doctor's identity and took Yomiel's body to the junkyard superintendent who was investigating Temsik radiation. Because his body suddenly went missing, Yomiel was delayed from meeting Beauty and Dandy in the Chicken Kitchen and then again in Kamila's old house before he found his body at last in the basement of the superintendent's office.
He then proceeds to blow up the contraption modelled after Kamila's birthday surprise for her mother in the basement in order to erase any evidence, of his powers existing killing the pigeon professor and injuring Cabanela badly. Then he dragged Cabanela up to the office and forced him to call the justice minister and demand Jowd's death with Kamila as his hostage before shooting him. Then he called Sith to talk about their pending deal before leaving for the S-Yonoa, the submarine that Sith was on to fetch him. Meanwhile, Sissel, who has been on a quest to discover his own lost memory, saves the two without his knowledge.
On the submarine, he left his body and possessed Kamila, unknowingly allowing Sith to betray him and take the Temsik fragment. Yomiel laid in wait for Jowd with a rifle, knowing he would come. He realised Sissel had been saving some people he was trying to kill and so decided he had to kill Jowd himself. But instead of Jowd, it was Lynne who came to find Kamila, and he threatened Lynne with the gun instead. Yomiel was about to kill Lynne when the whole submarine shook, and Lynne died trying to save Kamila before being saved by Sissel yet again.
Yomiel left Kamila as soon as he realised that the submarine was hit by its own torpedo and that he had been betrayed by Sith. Then, as the whole submarine slowly turned nose up and Lynne and Kamila were trapped and nearly drowned, he rescued them with his new body made of bits and pieces around the sub.
He talks to Lynne, Sissel, and Missile and tells them all about the powers of Temsik that he had learnt over the years. In the end though, they are still trapped in the submarine, and Lynne begun to understand and feel the despair and loneliness he did and she cried. At that moment, Yomiel no longer had the heart to exact revenge on anyone, because someone understood him. He simply wanted someone to feel like he did, the pain of being alone and lost, which was the real reason for his "revenge".
After that, Sissel raised a new hope. The control room had been detached for no apparent reason, so with the help of Cabanela's tracking device, Sissel, Missile and Yomiel (unbeknownst to the other two) travelled to the control room on the last torpedo and attempted to save Jowd, who had been shot and killed. They then realised they can go back ten years through Yomiel's body, which is now a normal corpse since it lost the Temsik fragment to Sith.
The four ghosts changed Yomiel's fate of being hit by the meteorite fragment, remaking the whole timeline. The fragment, deflected by a statue of Mino swapped into position, flew through Jowd's knee and unknowingly killed and lodged itself into the cat Sissel instead. The bullet that Jowd fires as a result was swapped for little Lynne's sweet potato, throwing Yomiel into the spike on the fountain's lamp and dropping little Lynne under the path of the falling Mino. The spirits of Sissel, Yomiel, and Missile then used all of their kinds of ghost tricks to earn enough time for Yomiel to manipulate his own past self to throw little Lynne out of the way, letting himself be half crushed under Mino instead, although he survives.
Jowd then proceeds to send Lynne to call the police to pick up Yomiel. Sissel is then found by Lynne when she comes back, and Jowd adopts the cat. Ghost Yomiel then hints that the cat is really Ghost Sissel's real identity, which allows him to regain his memories. Yomiel apologizes for killing Sissel, and they all travel back to the changed "present", erasing both Yomiel and Sissel's deaths.
After the timeline change, Yomiel is seen in prison for his crime of taking Lynne hostage, wearing the same violently pink smock Jowd was seen wearing, He was painting an artwork of Sissel in his prison cell, serving his sentence of ten years to its last day. His fiancee is still alive and waiting for him as he is released, and he thanks Sissel again before he leaves his cell.
Yomiel's ghost powers are far greater than Sissel's and Missile's because he had a chance to develop 10 years in the presence of Temsik radiation, something Ray didn't have.
- Possession: Yomiel can possess objects and living beings alike, both living and dead. His range to jump from object to object dwarfs even Missile's, whose range is already three times as large as that of Sissel- given the power of Yomiel's abilities, it's entirely possible that Yomiel has no range, and can simply teleport between objects at his will in the Ghost World. He is also shown to possess multiple objects at the same time, using them to form a temporary body.
- Manipulation: Yomiel is able to possess and completely take over humans and animals. Like this, he can force them to do something they would otherwise never do. People with a very strong will, like Lynne, can partially resist the possession.
- Trick: Like Sissel, he can manipulate some objects after being possessed. Players first sees him using his ghost tricks is when he tried to kill Inspector Cabanela.
- Phone line transportation: It is noted by Ray that Yomiel is able to move to other locations via phone lines, something he is unable to do.
Yomiel has also openly admitted that he is unable to go back in time. If he was able to do this, he would have saved his fiancee and Sissel- his own powers over time, as he explained, are permanently used in a passive fashion as the source of his immortality, seemingly confirming that even each Ghost Trick user's powers over time differ between individuals.