- Maria was born two weeks after Saki and like the latter, was born with her umbilical cord wrapped around her neck. On top of that, she was also a premature breech birth. Had the birthing assistant cut her umbilical cord a bit later, Maria would no doubt have died.
- The anime showed that Maria formally met Saki on their first day in Harmony School, and their childhood together. Satoru was also present, but as the montage was shown after the group had their memories altered, Shun was noticeably absent.
- During the summer camp, Maria is not captured by the Ground Spider colony of Queerats after having her Cantus sealed by Rijin, who died in the colony's attack. She successfully hides from them and later regained her Cantus like the rest of the group.
- After the first time skip, she and Saki begin dating, but she remains the object of Mamoru's adoration. Even while dating Saki, she remains affectionate to Mamoru, and appears to feel responsible for taking care of him. This is possibly due to how Mamoru has somewhat come to view her as his surrogate mother, since his own died in his childhood. She eventually forms a duty pair with Mamoru at Sage Academy.
- When the group discovered that their memories had been altered and sought to uncover the truth, Maria persuades Saki to keep their pursuit a secret from Mamoru, due to his delicate nature.
- Maria is the first to of the group to discover that Mamoru ran away from home. Together with Saki and Satoru, they follow his trail out of the Holy Barrier. When they find his sled at the foot of a cliff, Maria turns frantic thinking about how he might have been fatally injured. However, they find another trail and followed it to a snow cave where Mamoru was resting after being rescued by the Queerat Squonk. When Mamoru reveals the reason he ran away was because he had been targeted by a Tainted Cat, obviously for disposal, Maria supports his decision to leave.
- While Satoru and Saki return to the village, Maria stays behind to care for Mamoru. However, when the pair later returns to bring them back, Maria and Mamoru have disappeared, leaving behind a letter from Maria, informing the former of their decision to leave rather than be killed. In the letter, Maria requests that they not look for them and to tell the village leaders that they have died.
- After the second time skip, Saki discovers that two or three years after their disappearance, Maria and Mamoru's bones were presented to the Security Council by Yakomaru. Before being killed by the Robber Fly colony, Maria gave birth to a child which was taken away by the Queerats and raised as the Messiah to revolt against humanity.
- In the manga, Maria was the one targeted and Mamoru ran away with her. It is shown that they had Messiah before the Robber Fly colony threatened them when Saki came to visit. In the "Rest in Pieces!" extra, Maria mentions that Mamoru was not there to protect her when they took the Messiah.