Mayu Ikeda's History
Mayu's school's once hosted an open house, presumably for a festival, but Mayu's mother didn't attend and Mayu was very angry when she came back home. Mrs. Ikeda explained she was unable to come because Mayu's younger brother Satoru was sick. Feeling envious of her mother's constant attention towards her brother, she ran away but came back later. After returning to the apartment they live in, Mayu put her scarf over a radiator (something her mother told her not to do) and hides in the closet to get back at her mother for perceiving and for ignoring her, telling a still somewhat awake Satoru not to tell Mrs. Ikeda that she was there. The scarf caught fire and led to the apartment catching fire as well. Mrs. Ikeda came back from shopping and found her apartment on fire; she rushes in to save Satoru and got out safely, but since Satoru was unconscious at that time and unable to tell her that Mayu was still in the closet, she unfortunately did not know Mayu was still inside. By the time the firefighters found Mayu, it was too late; she had either burned to death or died of asphyxation.
However, this was not the end for Mayu. Mistakenly thinking that her mother had deliberately left her to die in the fire, Mayu's soul was not at peace as she was filled with hatred and resentment towards her family. Thus she could not pass on to the afterlife and became a vengeful ghost, intent on killing Satoru since she thought her mother loved him more than her, in what she believed to be revenge on her mother for (unknowingly) leaving her to die.
Mayu's existence as a ghost was maintained by a yōkai known as the Soul Piper (Tatarimokke), who looks after the souls of dead children until they can either accept their deaths and pass on, or to be sent to Hell if the child does wrong. It's eyes are usually closed, but every time Mayu committed a harmful act against her mother, brother or anyone, the Piper's eye opened slowly, symbolizing Mayu drawing closer to the point of no return.
Because of the fire, Satoru fell into a coma and remained in this state for about a year. He also happened to be close friends with Sōta, Kagome's little brother. When the Higurashi siblings visit Satoru in the hospital, Kagome has the ability to see Mayu in her spirit form, and finds her with the Soul Piper. She goes to Myōga to learn of the Soul Piper and returns to attempt saving Mayu's soul.
After learning the truth about what really happened during the fire from Mayu's grieving mother, the two of them catch Mayu as she's making yet another attempt to kill Satoru. She knocks Mrs. Ikeda unconscious but Kagome is able to get through to Mayu and she realizes that she was responsible for the fire. But claiming she still hates them both, Mayu tries to kill Satoru again, but he is saved by Inuyasha for his just-in-time arrival.
Before Mayu can do more, the Soul Piper appears behind her with its eyes fully open, signifying that Mayu is doomed to Hell because of all her hateful actions. Mayu protests as the Soul Piper wraps her up in chains, takes her away back to her apartment where she died, and subjects her to an illusion of how she died in the fire. As Mayu thinks on how it happened, Kagome soon arrives and tries to get Mayu to come with her but Mayu brushes her off not wanting her help.
(Around the same time, Satoru finally wakes up from the coma. As soon as he sees his mother, Satoru tells her that Mayu is inside the closet [logically, he doesn't know that a year has passed and Mayu is dead], and begs Mrs. Ikeda to go save her)
Moments later, a portal to Hell opens up in the floor and the chain still attached to Mayu's arm pulls her down into it, much to her terror. Kagome barely manages to grab Mayu's other arm as both girls holds on desperately, but the Soul Piper adds more force to the pull making it all too clear that it's only a matter of time before Mayu is dragged into Hell.
To save Mayu from Hell, Kagome tells Mayu she can't have it end like this and urges her to make up with her mother before she passes on for good. The desperate Mayu asks Kagome if her mom is still angry, and Kagome tells her that her mother does love her and always has, which causes Mayu to think back to all the happy times she had with her mother and realize it's true. Driven to tears, Mayu pleaded desperately for a chance to apologize.
Seeing Mayu's change of heart, the Soul Piper is pleased and decides to give Mayu a chance to atone and changed his judgement on her soul. Her chains break as the portal disappears, meaning Mayu has been spared from Hell.
The next day, Mrs. Ikeda returns to her old apartment and is confronted by the no longer angry Mayu's soul. Mayu apologizes to her and asks for her mother's forgiveness. Her mother lovingly forgives her and she says her final goodbye. Though still grief-stricken, Mrs. Ikeda is now more content having reconciled with her daughter. And due to that Mayu's soul was finally at peace.
Having atoned for her actions, Mayu is now able to ascend to Heaven. As a bonus, the Soul Piper allows her to remain for one more week until her brother comes home from the hospital. At this time, Mayu visited Kagome at her home wearing a beautiful goldfish yukata her mother had made her before her death. Mayu thanks Kagome for everything, and finally moves on.
As Kagome watches as Mayu departs with the Soul Piper, she thinks to herself on how Mayu was never an evil spirit as Myōga had claimed but merely an ordinary little girl who loves her mother more than anything.
