CHARACTER HISTORY: Matt is an extremely minor character in his canon, and not much information is given about his past, most of it coming from the supplementary informational book "How To Read," where we are told he comes from Wammy's House, an English orphanage for exceptional children. At Wammy's House, they are pushed to compete for the title of L's successor, the top detective in the world.
Matt was born on February 1, 1990. Due to the fact that Matt came from Wammy's House, we can assume that he was an orphan, though details of his history are unknown. I choose to play it that he was orphaned at a young age and was passed around to a few foster homes before his potential was noticed and he was sent to Wammy's House, probably settling in there somewhere between 6 and 8 years old. Once there, he would have been pushed from the start to reach his full potential. Most of the characters featured in the series that come from Wammy's House lack positive social skills - they are either ill-adjusted or manipulative, so it's pretty likely that they were primarily treated as students, and only secondarily as normal children, though they obviously had playtime and social interaction amongst themselves. Wammy's House residents are shown kicking balls around and otherwise playing, but it doesn't seem likely that they had a lot of concerned, individual loving attention. Matt was the third most intelligent student at Wammy's, but judging by the fact that his "intelligence" stat in the info book was lower than the two above him, and only slightly above other 'normal' characters in the series, the gap between him and Mello, the next highest, was probably quite a big gap. He likely didn't push himself very hard, slacked off or was otherwise hindered in some way, and he probably did a bit more playing than studying.
When L died, and Mello left the orphanage, abandoning his studies, Near was placed in the position of L's successor, and the pressure was off Matt. Somewhere between the ages of 14 and 19 (probably closer to 19), it's very likely he left the orphanage and took on some sort of job so he could live on his own. I imagine it was probably a job that fit his interests, and likely involved making, testing, or selling video games, and probably paid decently considering how he dresses and his addiction to video games. He may or may not have moved to the States, though I tend to think he would have stuck with what he knows, in England. When he was 19 years old, he was contacted by Mello, who was working on the case against Kira, a serial killer who supernaturally kills people that Kira considers criminals or useless to society, a case that L, the 'idol' of Wammy's House, died trying to solve, and which Mello was in fierce competition with Near, the other L successor, to get to the bottom of. Matt agreed to help Mello, and met him in the States, where Mello was camped out after being injured in a stand-off with some police officers. There must have been some compelling reason to get Matt to join Mello in such a dangerous mission, though I'm going to leave this vague since I don't want to write speculative shared history for another character. The most likely reasons, from my perspective, would be boredom on Matt's part, desire to solve the case, hatred of Near, or a friendship with Mello from orphanage days that he wanted to rekindle for some reason. I'd like to leave this vague and work it out with any Mello player who might apply in the future - I don't want to godmod history like that.
After joining Mello, Matt fell into place following orders, though they seemed to act familiar with each other, and Mello treated him as far more of an equal than he did with the other people he worked with previously, as well as trusting him more. This was probably because of their shared history at Wammy's House and possibly an old friendship. After meeting up, the first thing Matt and Mello did was find the police officers travelling to the States from Japan to help with the Kira case, finding the officers based on information previously given to Mello by a member of Near's police force. They tailed the officers to their destination, the place where Misa, a suspect to be Kira, was staying. Matt stayed behind while Mello continued on after another officer who was continuing to move. When Matt saw that it was Misa's place of residence, he let Mello know, and Mello bugged the room and conducted surveillance on Misa, while Matt watched over the police headquarters, where the other officer went. They maintained surveillance for quite some time, a task that Matt found boring, and at some point followed the group back to Japan. When Mello later discovered that Takada, a spokeswoman for Kira, was likely involved with Light Yagami, who he suspected of being Kira, and therefore had neccessary information, he formed a plan to kidnap her. Matt's function in this plan was to distract her bodyguards while Mello offered her a ride away from the scene on a motorbike, kidnapping her. Matt successfully distracted the bodyguards by shooting off a flare gun and creating a smokescreen, and then leading them on a car chase. Eventually he was surrounded by their many cars and, realizing he could no longer run, stepped out of his car expecting the bodyguards to keep him alive for questioning. However, this was a miscalculation, and he was shot multiple times against the side of the car. He died, cigarette still burning in his mouth.