Martha is the foster mother of Yusei Fudo, Jack Atlas, and Crow Hogan. She seems to be Hispanic and owns a cottage in the Satellite sector where she keeps care of orphaned and homeless children. Martha is regarded as a parental figure by all abandoned children in Satellite and refers to all of them as her children.
After Yusei Fudo sustains an injury from his Duel with Kalin Kessler, Crow takes him to Martha's refuge, so that he could receive the required surgery. As the gang are waiting outside for the operation to be over, Martha assists as a nurse to the doctor, who works on Yusei.
After Yusei wakes up, Martha scolds him for growing up as an adult, just so he could forget about his foster parents, as well as beginning the task of building his first Duel Runner. All of that, just so that he can put his life in danger by going to the B.A.D. Area to stop the Dark Signers without the help of his fellow Signers). She also tells him that she can't understand why he didn't ask for help from his friends, when Yusei's ideals happen to be "believing in friendship". Even so, she reminds Yusei that no matter what he does, he can always count on his friends that they will be there supporting and backing him up.
She's present when Akiza's father, Hideo, goes to Satellite in order to ask for his help. However, Yusei refuses to help as doubting that he really can do something for her. Martha figures out why as she says to him that his heart is all closed up now. This is due to the Duel against his old friend Kalin, as it left him with the fear of having to face against another friend. Martha tells Yusei that now the only ones who can help him are his friends. But in order for Yusei's heart to open again, he needs to face Akiza again as a friend. Before they leave, Martha teases Yusei, saying that "seeing that he likes Akiza, Yusei better go so that he can also get his future wife". Yusei tries to reject that opinion, but agrees to help nonetheless.
Later on, when all four Signers along with Leo, Trudge, and Mina go back to Satellite, they are greeted by Martha. She seems happy that Jack is finally back too. However, the reunion is cut short as Yusei finds out that Rally and the others, along with Crow, have disappeared. Martha then notices that Akiza is there as well, meaning that Yusei was able to open her closed heart after all. Thus as everyone is later seated on the table and having supper, Roman suddenly appears in order to Duel.
After Yusei has accepted to Duel, he's accompanied by Akiza, while Jack and the rest take Martha and the kids to a safer place. However, three of the children, Taka, John and Mitch, have decided to watch the Duel; Martha notices this and along with Trudge are gone looking for them to where Roman and Yusei's Duel is taking place.
As his spider geoglyph has formed on that area, she and Trudge eventually get near the Dueling site but away from the Nazca Line. As she notices Yusei, they both then see John and Mitch, who are scared and trapped inside the spider geoglyph. Just then they hear Akiza who says to them that an Earthbound Immortal is about to be summoned, and that the kids' souls will be sacrificed. Martha, worried now because of this, tells Yusei to protect them. However, with help from Jack and Trudge, Martha manages to save the children when Earthbound Immortal Uru is summoned.
The impact caused by the summoning and attacks of the Earthbound Immortal damages the building Martha, Trudge, and Taka were on. It slants and begins to fall over, and Martha crawls to the edge to save Taka. She manages to get Taka to Trudge, but falls off of the building and into the geoglyph and is sacrificed into Uru. Her last words were to Trudge, telling him to keep care of her children.
After Yusei and everyone else returns to her home, the children try to apologize for the occurring incident to Dr. Schmitt stating that it's their fault for what happened to her. However, Yusei states that it isn't and that the true culprits to blame are the Dark Signers. He then makes them believe that once the Dark Signers are defeated, Martha and everyone else will return.
After Yusei and Roman's second Duel ends with Yusei winning, she finally returns along with Rally, Tank, Nervin, Blitz and other people sacrificed to summon Uru.
Pre-World Racing Grand Prix
Martha and Schmidt try to convince a withdrawn old man, Bashford, to move in with them, due to the dangerous nature of his house. After failing to do so, the children in her care convince Crow to talk with Bashford. Crow, along with Yusei, Jack and Blister manage to talk him into coming to Martha's, where he will have plenty of grandchildren. Afterwards, Bashford makes a Stardust Dragon statue outside her house.
Later, after the Divine Temple appears, she and Blister help get the children on a bus, and head for safety. When the Children were worried, she assured them Yusei, Jack and Crow will protect the city. During the final Duel between Yusei and Z-one, she along with Dr. Schmidt, Blister and her children are cheering for Yusei.