MD-5

"We call ourselves MD-5, and our mission is to... TAKE DOWN THE EVIL CONGLOMERATE TAAAAAAASCOOOOOOOORP!" MD-5 is the main protagonistic group that rebels against TAS Corp. and more specifically its head, Derek Lucks.

The team originally comprised of Masa, Sofia, and Lamar but were joined a year later by Tari and Theo. However, following their failed attempt to hack TASCorp's server, Theo was held hostage by Lucks and Tari surrendered herself to him in order to save the others.

Six months later, Tari was able to make contact again and they were joined by Belle in order to stop Lucks. Despite succeeding in exposing Lucks' illegal activities, Masa unexplainedly shot him and was left with Belle as the police arrived while the others escaped the crime scene, before being discovered by Marco.

History
MD-5 was founded about a year before the events of the show by Masa to retaliate against TAS Corp. for the lives they destroyed, due to him believing Lucks had killed Lucinia following her unexplained disappearance.

Somewhere along the way, Masa was able to recruit Lucinia's younger sister, Sofia Porter and another Meta Runner, Lamar Williams. Despite their best efforts, any attempts to gather information and expose TASCorp were thwarted due to the company's high level of security.

Masa Shimamoto
The leader of the group and its founder. After being discharged from TASCorp due to hacking into Lucks' server for information of Lucinia Porter's unexplained disappearance, he began to realize that Lucks had something to do with her absence and began his campaign to expose TASCorp for its misdeeds. He has most likely been put under criminal charges after being framed for the death of Lucks.

Sofia Porter
The younger sister of Lucinia, whose disappearance caused the formation of the group. She is extremely talented in computers, hacking, and Meta Runner technology. She joined to help Masa take down TASCorp to find out what happened to her older sister.

Lamar Williams
A Meta Runner found by Masa and Sofia and a self-proclaimed otaku who joined the two for reasons unknown but shares their belief that TASCorp needs to pay for what it has done and has trusted them in their goal to take down Lucks.

Tari
An amneasic Meta Runner with a unique ability to enter the game she plays, due to somehow being involved in Project Blue. After being pursued by Lucks for her abilities, she joined the group for protection but later gave herself up to Lucks for her friends' freedom and was later rescued by Lamar and the others.

Theo
A video game character. He met in Ultra Jump Mania but was ejected out when TASCorp tried to study her Meta Runner Arm. His cartridge was destroyed and is sent to the containment chamber by Lucks. When he got in the server 2 times, he was sent to a "nightmare" game world. He was busted out by Tari in the Season 2 finale and is with MD-5 to restore Lucinia.

Belle Fontiere
She was a member of TASCorp. In Season 1, she was one of the main enemies of MD-5. As of "Heart to Heart", she learnt that Lucks lied about Lucinia's death and joined MD-5 to shut down TASCorp. She stayed with Masa after the accidental death of Lucks and her fate remains unknown.

Trivia

 * MD5 is the name of a hashing algorithm. Its strength is very weak compared to more modern hashing algorithms.