|This Mundane World|
|Original Air Date||November 1, 2008|
|Big Brother||My Teacher|
"This Mundane World" is the 5th episode of the season "Three Vessels" and the 57th episode from total.
As the episode begins, a girl with black hair and a rather dreamy look is walking along school carrying organs for the chemistry class. As she is about to turn at a corner she falls accidentally into Yuzuki, making a beaker fall and break. As Yuzuki helps the girl pick up the pieces, a teacher, Miwa Niiyama, approaches to check the situation. Yuzuki tries to explain that it's her fault that the beaker broke, but the girl, Katase Ririka, claims the blame is all hers. Miss Niiyama brushes the incident off casually, only telling them to be more careful and leaves with the rest of the chemistry organs. Yuzuki comments that Miss Niiyama has never been seen upset.
Despite her looks, Ichimokuren, in his conversation with Niiyama, comments that Ririka is good as a student, and Miss Niiyama expresses her belief that this is because her parents are good people. At night, while Miss Niiyama is correcting some tests, the phone rings. Niiyama picks it up, but no one is on the other line.
The next day at school, Miss Niiyama enters the teacher's office, but in response to her greeting everyone gives her a cold look. A teacher leads her to the headmaster's office. Along with the headmaster an old woman is sitting on a sofa, and the teacher who brought Niiyama in apologises to her for making her wait. Confused, Niiyama greets the old lady which is introduced by the headmaster as Ririka's grandmother. The response to her greeting is rather cold, and Niiyama is accused of falsely scolding Ririka because of Yuzuki's fault. As Niiyama denies she did so, the old lady calls her a liar.
Niiyama is forced to apologise for her "tyrannical" behaviour to the old lady, and when she tries to explain she is stopped by the rest of the teachers. Ririka's grandma doesn't seem to care about Niiyama hearing her when she speaks badly of her. After she leaves Niiyama decides to ask Ririka about the details after school. The rest of the teachers don't appear to have complete faith in her saying of being innocent.
After school Niiyama speaks to Ririka, who apologises for her grandmother's behaviour and promises to speak to her. The conversation is observed by Ichimokuren who uses his eye projection. In his conversation with the rest of Ai's companions, Ichimokuren appears to be the most worried about Niiyama's situation, and the group calls Ririka's grandmother a monster.
At 2 o'clock that night Niiyama receives another phone call. This time Ririka's grandmother responds and a pretty heated conversation starts. Niiyama is accused of threatening Ririka to prove her innocence. Ririka hears her grandmother talking and starts trembling in fear. Ririka's grandmother accuses Niiyama of trying to keep Yuzuki's record clean by burdening Ririka's, and states that she will not allow Ririka to go to school for a few days. Also, she once again refuses to listen to Niiyama's explanation. Niiyama closes the phone enraged and takes the cable off.
Next day the principal's assistant receives a complain-phone call from Ririka's grandmother, but are unable to do anything except comply to her demands. After school Ririka's grandmother even starts a campaign against Niiyama by giving broshures to students. As Niiyama returns home she finds a hole pile of broshures stacked on her door and in her mailbox. In a state of anger she contacts Hell Correspodence, but closes her PC before clicking on the link. Yuzuki sees this via a vision.
Back at the teacher's office, the teachers show sympathy towards Niiyama's situation and tells her to hang on for the time being. Niiyama however is unconvinved. After the meeting, Yuzuki meets Niiyama and tries to apologise for the situation, however Niiyama assures her that no one was at fault for that. She concludes by saying that reality seems to take the place of the ideals in society.
As promised to Yuzuki, Niiyama visits Ririka's house in order to solve the misunderstanding problem. Security of the house is tight. Ririka opens the door and makes tea for Niiyama. She explains that her grandmother isn't truly an evil person, however she is very overprotective and needs to make someone the villain. At that time Ririka's grandmother returns, and is enraged by Niiyama being in the house. Much to Niiyama's shock, it is revealed that Ririka had been lying to her grandmother all along, accusing Niiyama.
Ririka meets Niiyama outside the house and apologizes to her, saying that she is forced to lie. Niiyama says that only she can solve this problem by telling the truth. However Ririka doesn't accept that since she thinks adults can solve their problems by themselves. Enraged, Niiyama contacts Hell Correspodence immediately, and is given Yamawaro's doll. Ai asks her if it is okay to go to hell because of a student, and Niiyama replies that she is tired of being taken lightly because she is a teacher, and that teachers are responsible to students, not to the parents. After that, she pulls the string.
Ririka disappears and her grandmother is startled and begins looking around for her. As Niiyama walks by Ririka's house the next day, she sees Ririka's grandmother looking outside the window, with a blank look in her eyes. She crosses paths with Yuzuki, who notices the hell-bound tattoo on Niiyama's chest.