Mello and Near were raised at Wammy's House - an orphanage for gifted children in Winchester, England. They were designated to being L's successors and after his death, Roger (the orphanage manager) communicates Mello and Near about L's death, telling both that L failed to choose a successor. So Roger suggested that they work together, but Mello refuses to work with Near. Mello leaves Wammy's House with the goal of finding Kira in his own way. Sometime after leaving the orphanage, Mello goes to America, where it joins forces with the Mafia. After a while, Near also leaves the orphanage and goes to America, becoming head of the SPK.
Almost four years after L's death, Mello learns about the Death Note, since a member of the newly formed SPK leaked information to him. After some conflicts involving Mello, Near suspects there may be a spy within the SPK, so he plans to find out who is leaking information to Mello. Shortly thereafter getting the Death Note, Mello has a member of the Mafia write down the names of almost every member of the SPK in Death Note, not only to severely hamper Near's investigation and reduce the number of his resources, but also to kill the spy within the SPK. Near and the second L agree to share information, causing Mello's defeat.
A while later, Mello and Near meet briefly for the first time after years. In this brief meeting, Near gives Mello the photograph that which he kept, and in return Mello tells him about the Shinigami and the fake Death Note rules. Each wryly promises the other that the race is on to see who finds Kira first. In the end, Mello is killed after his name was written on a piece of the Death Note. During the final confrontation, Near credits Mello as the single most pivotal person in exposing Light's plans and thus bringing about his subsequent defeat. Near declares that he and Mello have managed not only to match their idol, the original L, but also surpass him and avenge his death by obtaining the evidence that leads to the downfall of Kira. After bringing down Kira, Near officially becomes the new L. He is later shown eating a chocolate bar, paying homage to Mello with his favorite snack.
Both in Anime/Manga, Mello and Near are represented having a rivalry. The artist of Death Note, Takeshi Obata, points out in Death Note 13: How to Read that Mello's envy and hatred of Near is only one-sided and that Near honestly liked Mello.
When Mello receives his childhood photo from Near. On the back, Near has written "Dear Mello". This is a fact that intrigues shippers.
In some fanfictions, their relationship is portrayed more profoundly. It has been confirmed and it's evident that Near likes Mello and doesn't see him as a rival. So this one-sided relationship between them is greatly explored. Both characters have opposite and unique personalities which is useful in developing different plots in fanfictions.
- "Mello" in Japanese is Mero and "Near" in Japanese is Nia. That's why this ship is called Meronia.