One Girl's Day is the sixth chapter of Higanbana no Saku Yoru ni - Dai Ichi Ya (彼岸花の咲く夜に 第一夜).
Running late for school, Yoko Numata is tripped by a non-visible Higanbana, which results in her skinning her knee before reaching the school. Marie criticizes Higanbana for it with Higanbana saying it is an everyday experience someone should experience at least once. Not knowing that Marie and Higanbana are watching her, Yoko gets up and tries to run to the school. The bell rings and the gates close. She is officially late for class. Defeated, she decides to simply walk to class. Higanbana comments on Yoko's day so far and Marie urges her to stop messing with Yoko. Higanbana looks to the school building. Yoko's teacher is taking roll call, Yoko yells her name which prompts the rest of the class to do so. When it is time to turn in homework, Higanbana takes Yoko's homework from her. After going through her things and swearing she did her homework, Yoko is sent to the front of the class alongside others for forgetting their homework. She ponders where she left her homework while other students were receiving a punishment. When Yoko gets to the teacher, she is punished for forgetting their homework by having her cheeks stretched and twisted with the rest of the class laughing. Yoko looks at it and finds it fun and returns to her seat. Marie feels sympathetic towards Yoko. However, Higanbana states she is testing Yoko on if things are still fun despite having bad luck throughout the day. Marie sighs and stays quiet, to not interrupt Higanbana's good mood. Higanbana proclaims that no matter what she will push Yoko to her limits on if she is having a "fun" time.
Yoko proceeds to have a series of unfortunate events throughout the day caused by Higanbana. While sleeping in class, Yoko is awoken by a teacher who asked for what page they were on in her textbook. A student behind her helps her as the class has become impatient. Despite being in trouble for falling asleep, she has a wonderful feeling and was happy with it. In science class, her test tube shatters due to the thermometer being slippery. Her teacher was mad at her, but she still had fun regardless due to the thermometer squirting out like a water gun and everyone laughed. At lunch, while drinking milk, the milk went up Yoko's nose and she sneezed it out with milking oozing from her nose in a line. Everyone in her class laughed. Other students start spurting milk out of their nose and the whole class laughed. Marie comments that the milk is a bit too far, while Higanbana is more determined to make sure that Yoko cries from the bad day. During an afternoon break, Yoko while rushing outside collides into a now-visible Higanbana. Yoko is injured from the collision. She slowly gets dizzy and becomes unconscious due to blood loss. Marie objects to the scene saying Higanbana took things too far. However, Higanbana points out that the injury is not life-threatening and states that no matter what, she wants to see Yoko cry. Yoko is then taken to the infirmary.
The Nurse tells the others that she is fine and just lost consciousness due to blood loss. Yoko reflects on her injury and her day not exactly being the best. The P.E. bell rings and she laments on that she should be spending her day outside and playing and not in the infirmary. Yoko wakes and tries to convince the nurse to let her go. The nurse informs Yoko that she should try to sleep more. Yoko's homeroom teacher visits the infirmary and chastises Yoko for running in the hall. The nurse claims that Yoko will be able to return to class soon enough. Yoko protests that she wishes to return to class but the nurse rejects it. Yoko hears the other students in the courtyard cheering and yelling and Yoko becomes sad due to her being stuck in the infirmary. Higanbana is elated that she finally won. Marie sighs, losing respect for Higanbana.
Yoko laments on the fact she can hear her classmates playing in the distance but cannot see them and hates it. Commenting she was like a ghost that no one could see her, the nurse steps out of the infirmary and Yoko commenting that she wants to rejoin her classmates, tries to sneak out of the infirmary to head back to her classroom. She successfully gets to her classroom with her classmates worried about her and commenting on her injury and bandages. While everyone urged her to rest, Yoko assisted with cleaning in the science room. The students played in the room instead of cleaning and Takeshi becomes annoyed with his classmates. Yuko's broom got caught on a human anatomy dummy and it fell to the floor, breaking it into several pieces. Yoko apologizes to Takeshi for playing in the room and they all went to the teacher's room where the Nurse was there. They apologize to the teacher for breaking the anatomy dummy and Yoko gets scolded for leaving the infirmary. They return to homeroom and school ends. Yoko says goodbye to everyone in her class as everyone leaves for home. She proceeds to go to the roof to meet with Higanbana and Marie. Marie asks how Yoko's day was and Higanbana comments on the amount of trouble she has had today. Yoko says while she has had lots of trouble today, she said she had fun regardless. Higanbana admits defeat and Yoko comments that being a ghost was quite boring, with Higanbana commenting on how it's also the same story with Youkai. Yoko looks upon children playing in the courtyard and said that her day was really fun and wished she paid more attention in life. She is happy with her life. Higanbana asked if she kept her promise with Yoko replying yes. Marie asked if Higanbana intends to eat Yoko and she replies that she did it so she could experience school-life once again and that she would eat her. Marie regrets not being able to save Yoko. Yoko assures Marie that it is okay. Yoko's body crumbles and turns to a white soul, Higanbana snatches Yoko's soul and Marie decides to leave to not see Yoko's soul be consumed by Higanbana. Higanbana tastes Yoko's soul and dislikes the taste and leaves it to go to the afterlife.