Rika stares at her food in disdain, observant of how none of it appeals to her tastes and she gets up to toss it. Her friend stops to point out that she ate none of it but Rika can't help it if she doesn't like them. She doesn't like milk, several vegetables and meat, and several other items. If it was candy and sweets that'd be different. As she thinks about this her teacher stops her before she can dump the tray and takes the still-wrapped raisin bread she didn't touch, forcing her to take it while scolding her.
Annoyed by this, Rika tries to determine how she could get rid of it when she suddenly bumps into an old doll that's been in their classroom for years. Her friend sees her discard the bread and brings up that Mary, the doll, was even there when her sister attended the school. As a joke Rika politely offers the bread to the doll, she is shocked upon returning from gym class when she finds a large bite taken out of it. A few other classmates join her when one of them points out that Mary must have eaten it and recalls a story he was told, of Mary once eating the class fish. Rika's friend berates the boy as she stares at Mary, then quickly slides her into her backpack.
That evening, Rika is once again left in a foul mood seeing what her mother prepared and as her mother launches into yet another rant about the importance of food, she takes Mary out and sets her on the floor. With her mother distracted, she slides the food onto the floor- just in time for her mother to notice she isn't listening. But when she comes over to find the plate empty and no sign of the food being hidden, she makes a bewildered remark and walks away with the dirty dishes. Delighted, Rika returns to her room and hugs Mary while making fun of her mothers expression from moments ago. She then decides to hang onto Mary for now, realizing that if she can keep plying her with food then everyone will get off of her back about eating and she won't need to worry about feeding herself with foods she hates. Everyone would be so impressed.
The following day Rika is shown to put her plan into effect. She casually discards her foods to the floor for Mary and surprises her entire class, including her teacher, who even gives her a reward for being more thoughtful of her health. Her friend expresses surprise to see this "sudden change", and asks how she managed, but after teasingly responding to it, Rika starts to think of how strange it is that she has yet to feel hungry- despite giving everything to Mary. Not only that but Mary has been looking brand new.
One day, Rika prepares to leave for school when her mom stops her to bring up how impressed her Teacher was. He called a little while ago to tell her about the reward she was given, which makes her very happy. However, as Rika leaves for school she suddenly begins to wonder if it's really such a bad thing if everyone is happy, asking Mary what she thinks before feeling a hint of guilt. She hides her as a friend joins, delightfully announcing to Rika that she managed to conquer her hatred of mushrooms and can eat them with no problem now. Surprised, Rika asks how she did this; only to get the same response that she gave to her the other day. She runs off and Rika remains in her spot, realizing that with everyone else giving their best she hasn't been putting in much effort herself.
She decides for today to just not use Mary, and during lunch she forces herself to eat the meal given to her, pushing herself to finish as her friend remarks on how slowly she's eating today. She tearfully recoils after choking down the remainder of food and her Teacher approaches to show support, causing Rika to cheer up as she realizes how much she enjoys this feeling of being complimented knowing she deserved it.
Knowing this, Rika continues to put in the honest effort of eating the foods she dislikes so much. Her mother and classmates are shown to give her support to keep her going. She even returns Mary to class upon realizing she's no longer needed.
Then one day, during gym class Rika struggles to keep up with the rest of the class and can't understand her suddenly low stamina considering she's been eating so much. However she hasn't been feeling hungry either. It's then her friend mentions how sickly she looks and feeling her body lock up, Rika falls to the ground, momentarily paralyzed. Her friends run off to get help as she is left helplessly thinking, realizing something is wrong. She is taken to the nurses office and appears to be fine again, and with everyone still outside she returns to class, startled to find bite marks covering her desk and her items. She looks over to Mary, wondering how she could have done this as her friends return to check up on her due to being so worried. Rika attempts to speak about Mary and what happened, but when one her friends panics seeing how strange her hand looks, Rika is frightened noticing to see how much it resembles that of a dolls and finds that it extends to her arms. Her friends worriedly watch as she freaks out, yelling at Mary and throwing a book at her before running from the room.
At home Rika rushes inside, calling her mother for help- but she only finds Mary observing her from the dinner table. Rika begins to plead with Mary to end this and resume feeding her, unable to make sense of whats going on. She starts to hear a strange, pulsating beat. As she looks at Mary again she realizes it's a heartbeat before becoming aware of her own slowing down and growing quiet until she loses consciousness.
Hours pass when Rika awakens again. She realizes she had just experienced a horrible dream as she spots her mother nearby in the middle of making breakfast. She happily calls out to her and attempts to move forward, but for some reason she can't. Trying to determine what happened, she is shocked to find a girl with curled pigtails wearing a fancy outfit walk into the room to greet her mother. In return her mother greets "Rika", much to the real Rika's alarm. She desperately tries to call out for her mother but they go unnoticed as she remarks on how happy she is with Rika's pickiness being gone. She's been able to experiment with cooking lately and has a lot of fun now. "Rika" giggles and recalls what her mother said a few days ago, that "Eating is Living" and begins to enjoy the meal as the real Rika, now a doll on her shelf can only shed a single tear.
- Affectionate Gesture to the Head: Rika receives a pat on the head from her teacher when he praises her for working hard to finish her meals. The gesture makes her happy and she becomes more determined to do her best.
- And I Must Scream: Rika, trapped in a doll's body at the end of the story.
- Body Horror: As Rika starts to transform into a doll, her limbs become stiff and jointed like a doll's, and she loses the ability to move around on her own and even speak.
- Creepy Doll: The titular character, an old doll that ingests food.
- The Doll Episode: This is not the only story to feature dolls, but it is the first one.
- Girlish Pigtails: Both Rika and Mary have them. As part of her design, Mary's are styled into ringlets.
- Hope Spot: Rika begins making an honest effort to eat all her meals when she begins to get praise for it, leading readers to think that the story might end on a high note.
- Happens again during the end of the story, when Rikka awakens and sees her mom cooking after having passed out.
- Humanity Ensues: Mary at the end of the story.
- Kill and Replace: Sorta. Rika's not killed as much as she's turned into a doll and Mary becomes a human in her place.
- Meaningful Echo: "Eating is living" - said by Rika's mother when trying to get her to eat, and then repeated by Mary after ingesting enough food has caused her to come to life as a human.
- Parents Know Their Children: Averted. Rika's mother fully believes that the transformed Mary is Rikka, and pays no mind to the doll that suddenly showed up on the shelf.
- Picky Eater: Rika is so picky with food that she has a Long List of things she won't eat!
- Single Tear: The chapter ends with Rika shedding one.
- Sweet Tooth: Apparently the only kind of food Rika isn't picky about are candies and sweets.