Maria is a sweet and clean-cut girl down the street, which is a contrast of Brandon Heat's bad-boy image.
Maria was adopted by Jester (Maria's uncle) who accidentally killed her family when she was a baby. Feeling guilty for what he had done, he adopted Maria and raised her strictly.
Maria first met Brandon when she was attacked by by a group of thugs trying to rape her. Brandon saves her from the assault and Maria thanks him. The two began to date afterwards; Maria often worries about Brandon getting into street fights with his friends and tries to convince him to get a real job that her uncle could help him but he refuses since he sees it as leaving and betraying his friends.
Throughout the series, Maria makes her feelings for Brandon very clear. When her uncle was killed by Mad Dog Ladd, Mr. Asagi introduces himself as her uncle's friend and offers her to stay in his mansion. Maria accepts Mr. Asagi's offer to live with him,Maria is unaware that she is moving into the home of Big Daddy, Boss of Millennium. Brandon follows her and joins Millennium in hopes of being close to her and for a while it works out.Five years later, Maria grew her hair long and she has a job as a secretary, but she couldn't afford a place on her own and continues to stay with Big Daddy as the job wage is low. It is when Brandon becomes a sweeper that their relationship crumbles. He finds it harder and harder to face Maria with every person he kills, and soon he stops visiting her altogether. Maria eventually figures out what is going on, but wishes for his happiness nonetheless.
Three years later, with Brandon absorbed by his work, Big Daddy sees Maria's plight and sets her up to meet the man she loves. However, Brandon affirms his job and responsibilities, knowing that the danger of it would pose a danger to her as well, and chooses to leave Maria heartbroken, but considerably safer.Eventually Maria marries Big Daddy and becomes pregnant with his child. Big Daddy later informs her of Brandon's death. Devastated, she visits Brandon's grave, where she meets Brandon's former co-workers, who reveal to her Brandon had betrayed the organization which results in his death. She confronted Big Daddy who told her that Harry is the one who killed him. Startled by this she decides to visit Harry to talk to him and kill him for revenge. Luckily, Big Daddy stops her, begging her not to take revenge and reveals that Brandon is still alive but in hiding, offering Maria immense relief. Big Daddy then decides to confront Harry, but it results in his death. Harry then decides to get rid of everything that reminds him of Big Daddy.
Thirteen years later, Maria lives with her daughter Mika and Big Daddy's butler Tokioka. Maria and Mika have a very close bond together. Maria was living happily with her daughter and decides not to tell Mika about Millennion or that her father was head of the organization since she was hiding from them and protecting Mika. Millennion eventually discovers where they were hiding and proceeds to kill them but Maria instructs Tokioka to carry Mika to Brandon to protect her from Harry. Maria fought back with a shotgun while Mika and Tokioka try to escape. As they escape, Mika witnesses Maria got killed and cried out for her. As Maria dies, she sees Big Daddy's ghost, who help her cross over to the next world. Maria hopes that Mika gets to Brandon safely.
- The game hints at Brandon Heat's relationship with Maria through Mika Asagi's dialogue with Grave, in which Mika wonders if Grave was once friends with Maria.