Mello is portrayed as a young man with chin-length golden-blond hair and striking blue eyes. His bangs fall just above his eyebrows, and his height is roughly average. After an explosion at a Mafia hideout, which he triggers to avoid capture, Mello acquires a noticeable scar that stretches from somewhere between his shoulder and waist up to just below his nose and across his left eye. His typical attire consists of dark leather outfits. In the manga, Mello is shown wearing a distinctive red rosary and a bracelet adorned with a cross. However, in the anime adaptation, the cross is altered to appear as a stick, with the horizontal bar omitted. Additionally, he wears a belt with cross-shaped buckles and carries a gun attached to it. In the manga, this gun features a cross dangling from a chain on its handle.

Mello is introduced as a young teenager living at Wammy’s House, an orphanage for gifted children. Early on, he is seen outside playing with the other kids, at one point hitting another child on the head with a soccer ball, while Near remains indoors, occupied with a blank puzzle. When the children return inside, Mello is shown holding back a younger boy. Shortly after, the orphanage manager, Roger Ruvie, calls both Mello and Near to his office, where he informs them of L’s death.

Mello is visibly shocked and angered by the news, particularly when he learns that L had not chosen either him or Near as his successor. Roger suggests that the two work together to capture Kira, but while Near is open to the idea, Mello strongly rejects it. He points out that despite his efforts, Near always surpasses him in knowledge and ability, and the two have never been able to get along. With a mixture of frustration and resignation, Mello suggests that Near should take L’s place, and shortly afterward, he leaves Wammy’s House, determined to track down Kira on his own terms.

After leaving the orphanage, Mello eventually makes his way to America. Three years later, he aligns himself with Rod Ross, a high-ranking member of the Mafia. Mello quickly proves his value by eliminating crime figures that even Kira could not identify, gaining Ross’s trust. With Mello’s strategic guidance, Ross agrees to help him acquire the Death Note.

Nearly four years after L’s death, Mello learns about the Death Note from Ill Ratt, a member of the Special Provision for Kira (SPK), a group led by Near that is also investigating Kira. Ratt keeps Mello informed about the SPK’s plans.

Initially, Mello uses the Mafia to kidnap Kanichi Takimura, the Director of the Japanese NPA, hoping to exchange him for the Death Note, which is in the hands of the Japanese Task Force. When Takimura is mysteriously killed, Mello recognizes this as Kira’s doing and deduces that Kira likely has access to police information. To escalate the pressure, Mello kidnaps Sayu Yagami, the daughter of Deputy Director Soichiro Yagami, and demands that Soichiro come to the U.S. and hand over the Death Note. The notebook is sent in a missile that cannot be tracked by radar, eventually falling into the ocean, where Mello’s group retrieves it before the authorities can react. Throughout this ordeal, Mello eats chocolate while communicating with Soichiro, which Near takes as a subtle sign that Mello has succeeded in obtaining the Death Note.

Mello then forces a member of the Mafia to write the names of almost all the SPK members into the Death Note, aiming to cripple Near’s investigation and eliminate the SPK’s spy. He also threatens to kill Soichiro and Sayu unless the real name of the current L, Light Yagami, is revealed. The Task Force manages to buy time by falsely naming Touta Matsuda as L, and Mello, recognizing Matsuda as a puppet, decides not to kill him.

Mello also blackmails U.S. President David Hoope into granting him access to satellite surveillance, weaponry, funds, and information about the SPK. After learning the SPK has narrowed down his location, Mello relocates. Meanwhile, the Shinigami Sidoh, the original owner of the Death Note in Mello’s possession, tracks him down and causes panic among the Mafia members. Mello, however, remains calm and negotiates with Sidoh, instructing him to protect the hideout from potential attacks by the SPK.

Sidoh reveals to Mello that two of the Death Note’s rules, including the one stating that a user must kill someone within 13 days or die, are false. Mello quickly realizes that Kira likely used this rule to trick the Japanese police into believing he was innocent. Mello then forces Mafia member Jack Neylon to make the Shinigami Eye deal with Sidoh.

Light Yagami later discovers Mello’s location using Misa Amane’s Shinigami Eyes to identify Neylon, the current holder of the Death Note. Light sends a U.S. Army Special Forces team to raid Mello’s hideout, but Sidoh helps Mello and his associates escape, leaving only one surviving soldier, who takes his own life. However, Mello’s hideout is located again, this time by the Kira Task Force led by Soichiro Yagami, who has made the Shinigami Eye deal with Ryuk. During the raid, most of the Mafia members are killed, but Mello escapes after detonating explosives, leaving him scarred along the left side of his face.

Mello later takes refuge in New York, at the home of SPK member Halle Lidner, who keeps him informed about Near’s progress. Lidner believes that both Mello and Near are essential to capturing Kira, even if they fail to cooperate. Mello eventually infiltrates SPK headquarters, holding Lidner at gunpoint. He demands the only existing photograph of himself from Near. Near acknowledges Mello’s role in helping his investigation, which enrages Mello. He turns his gun on Near, but Lidner intervenes, convincing him not to shoot. Near then hands over the photograph, and in exchange, Mello informs Near about the Shinigami and the fake Death Note rules. As Mello departs, both vow to see who will catch Kira first. This meeting significantly sharpens Near’s suspicions of Light Yagami.

Mello later lures Kanzo Mogi of the Japanese Task Force to New York, where he is captured by Near and the SPK. Near and Mello’s conversation, as well as other developments, cause Mogi and Shuichi Aizawa to question whether Light Yagami could be Kira. Eventually, Aizawa meets with Near and provides further information about the Death Note. Lidner passes this information on to Mello, except for Near’s discovery that Light is the new L and the prime suspect for Kira.

Joined by his childhood friend Matt, Mello follows Aizawa and Mogi back to Los Angeles, where they spy on Misa Amane and the Task Force. Mello suspects Misa is the Second Kira, though her airheaded behavior makes him doubt Kira would have willingly allied with her. Nevertheless, he concludes that her boyfriend, Light Yagami, is indeed L.

Mello and Matt later follow the Task Force back to Japan, where they continue their investigation of Kiyomi Takada, a news anchor who has been chosen as Kira’s new spokesperson. Mello had originally planned to steal the Death Note from Misa but concludes that she is no longer the Second Kira.

Mello eventually kidnaps Kiyomi Takada with Matt’s assistance. After a chase, Mello successfully evades Takada’s guards and locks her in a shipping truck. However, Takada has hidden a piece of the Death Note in her clothing, and knowing Mello’s real name from Light, she uses it to kill him.

Influence After Death

Mello’s death proves to be a crucial turning point in the battle against Kira. Upon learning of Takada’s kidnapping, Teru Mikami, the current Kira, uses the Death Note to make her kill herself and destroy the evidence by setting fire to the truck. Unknown to Mikami, Light had also written the same instructions in his own Death Note moments earlier. This act of Mikami retrieving his Death Note from a bank deposit box is a critical breach in his usual routine. Near’s agent, Gevanni, notices the irregularity and is able to track down the real Death Note, allowing Near to expose Light Yagami as Kira and bring him to justice.

During the final confrontation with Light, Near credits Mello’s actions as the key factor in Kira’s downfall. Although Near doubts that Mello anticipated this outcome, he acknowledges that their combined efforts not only matched the original L but ultimately surpassed him, leading to Kira’s defeat.

In a final nod to Mello, Near is later seen eating a chocolate bar, a subtle tribute to his fallen rival.

Novel
Mello serves as the narrator for the Death Note spinoff novelDeath Note: Another Note: The Los Angeles BB Murder Cases. In this story, Mello explains that his purpose for narrating is to flaunt his superior knowledge of L compared to Near, even going so far as to refer to Near as a “big-headed twit.” Mello acknowledges that Near may not be the only person to read the story, so he attempts to make it more engaging. Throughout the novel, Mello shifts between traditional narration and a more casual, live storytelling style, which he claims helps him avoid boredom. The novel alternates between Mello’s commentary and Naomi Misora’s perspective as she investigates the BB murder cases.

TV Drama
In theDeath Notetelevision drama, Mello is portrayed as a split personality within Near. Initially, Mello is represented as a puppet that Near carries, but eventually, he manifests directly as part of Near’s psyche. Mello is depicted as more aggressive and volatile, in stark contrast to Near’s calm and methodical nature. At times, L scolds Mello when his actions interfere with Near’s investigations. Following L’s death, Mello begins to dominate Near’s personality, taking more extreme measures to capture Kira. However, it is later revealed that this shift in personality was a strategic move by Near to provoke Light into exposing himself as Kira. The Task Force and the police were aware of the plan, suggesting that Near has some control over when Mello’s personality emerges, although it is unclear whether this ability to switch has always existed or is a recent development.

Film Series
Mello does not make a direct appearance in theDeath Notelive-action film series but is acknowledged within the continuity. In the second episode of the mini-seriesDeath Note: New Generation, Ryuzaki asks Near about Mello, to which Near responds that Mello is his personal concern.