Eri is in college now. When she is walking in the campus, a male student invites her to drink tea with him.
Eri: I don't want to drink tea.
Student: Then how about talking with me?
Eri: What do you want to talk about?
Student: About our favourite TV programs, movies or the like. I've got all the booklets of movies that I've seen since I was three.
Eri: I don't love anything, so I'm not interested in movies. Bye.
The next time, he asks Eri if she wants to hear about Hokkaido, which is his hometown. Eri doesn't want to hear about Hokkaido. When he sees Eri the next time, he invites Eri to walk with him.
Eri: Then can I go to your place?
Student: My room is too messy for you to come. Please come to my place some other time.
Eri: I don't care how messy it is.
Student: But I think my room's too dirty for you to come.
Eri: I see. Bye.
Student: Ok. Let's go to my place.
Arriving at the room, the student starts cleaning the room. Eri watches the room in the meantime.
Eri loves just one thing. She loves a messy room of someone else. Suddenly, the student hugs Eri. Eri tells him she doesn't want him to do that, and she kicks him. She gets angry at him and goes home.
The next day, the student makes an apology to her. He says he wants her to forgive him because he thinks he can invite her again to drink tea together if she forgives him. He says "I'm sorry" over and over.
"I'll forgive you if you don't lock the door of your room for a month, and if whenever I get into your room, you don't care about me at all. It's impossible, isn't it? Bye." says Eri.
"I'll do that!" says the student. "I won't lock the door from today. You can come to my place any time."
Eri wonders why she said such a thing to him. Eri doesn't expect a miracle to happen again.
When Eri was a kindergarten kid and lived in an apartment with her parents, Mr. Shikamori was living in the next flat to theirs. He never locked the door of his flat. Looking into his room, Eri found it very messy. Mr. Shikamori was a journalist. Eri was able to write "Shikamori" in kanji even though she wasn't able to write her own name.
One evening, when Eri's mother came back from work, she heard Eri crying in Mr. Shikamori's flat. Eri said the room became messier when she tried to fix it. Eri's mother said to her Eri was going to be arrested by the police because she got into his flat. Even though Eri's mother wanted to apologize to Mr. Shikamori, he didn't come back that night.
The next morning, Eri's father found Mr. Shikamori sleeping outside his flat. Eri's father thought his room was too messy for him to sleep in. Alarm clock woke him up. Eri's mother makes an apology to him. He didn't care if Eri got into his room. He said to Eri, "You can play in my room. Your clothes will be ruined, though." He left for work without locking his flat. Eri's mother told Eri not to get into his room.
Eri got into Mr. Shikamori's room. There were many books scattered, a cup with leftover coffee, an ashtray with ash, piled dust and so on. There was a spider, too. A spider ordered nothing, it only waited for a victim to come. Eri felt relaxed. Dust was being piled freely. The room was totally different from Eri's place, where everything was in order. Eri went into the room almost every day secretly. She sometimes ate sweets there. Mr. Shikamori smiled when he sometimes found sweet dust in his room.
One Sunday, Eri and her mother heard Mr. Shikamori speaking with his girlfriend over the phone. Mr. Shikamori started cleaning the room to welcome her. Eri didn't want him to clean the room. Even though Eri's mother invited her to go out, she refused it and played in front of Mr. Shikamori's flat. Mr. Shikamori's girlfriend closed and locked the door. She often visited him since then and ended up living with him. When she said to Eri, "Good morning! Are you in kindergarten?" Eri ran away without saying anything. Eri's mother said to Eri "How embarrassing it was not to greet back to her."
Eri was in bad mood until one day she found Mr. Shikamori's door unlocked. She wondered if the woman wasn't in the room and got into the room. When Eri was to get out of the room seeing the woman, the woman told her not to go home. She said "I heard this room has been the place for you to play at. You can feel free to play here. I work here as I like. Ok?" The room was fixed and cleaned then. "I wonder where the spider's gone." murmured Eri. "I am the spider." said the woman. Eri thought it would be ok being in the room together with her because she was the spider.
The door of the next flat had been unlocked since then. Eri got into the room and enjoyed watching the room. Whenever the woman drank tea, she prepared two cups of tea. She put a cup of tea in front of Eri, and she drank the other cup of tea. The woman didn't care if Eri drank it or not. Eri sometimes just enjoyed watching the vapor changing its shape. Eri loved the time like this.
One day, the woman died in a traffic accident. Mr. Shikamori broke down and wept. Eri saw a man weeping loudly for the first time. Eri wasn't able to do anything for him. Dust was being piled in his room. Eri's parents found a better flat and decided to move there. Even though Eri didn't want to move house, she moved to another flat leaving Mr. Shikamori's sad flat behind. Eri went back to the apartment alone some days after she moved house. She found out that Mr. Shikamori also had moved house. Eri got that she had lost the liberated area.
The student is surprised that Eri really gets into his place. He has difficulty in neglecting her. Eri goes home immediately because she can't feel relaxed there. Eri's mother asks Eri what kind of job she wants to find after she graduates from the college. She doesn't have any particular job to do. She doesn't have any hobby, desire, or purpose. She thinks she can live for the rest of her life if she only has a small liberated area.
She goes to the student's room again. He is listening to the music with earphones. He tries to focus on listening to the music, but he wants her to talk to him, and he wants to serve coffee for her. She goes home immediately. He ends up deciding to stay away from home as long as he can. When she regrets she has annoyed him and decides to tell him to lock the door, two policemen tell her he was burgled.
Eri visits him. He is in the room, which is empty. When getting into the room, she says "Excuse me. May I come in?" He is surprised to hear her greet and wonders if he can greet back to her. "Here's a million yen. It's my fault that you were burgled. Please have it as compensation. I've never spent allowance or new year gift, that's why I have a million yen." says Eri to him. He is surprised to hear that. Eri says "However, I regret you must have lost something precious that you can't regain by money. I apologize." He says "It's not your fault. Burglars come even if the door is locked. But I'll be happy if you lend me 200, 000 yen. Actually, I've been at a loss because I'm broke. I will be giving it back to you on the pay day."
Eri has no intention of receiving the 200, 000 yen from him. She hears he has three part time jobs now. She suddenly gets worried that he might keep the door unlocked and goes to his place. She finds the door unlocked. He was sleeping in the room. She decides to stay there until he wakes up in case a burglar comes again. The atmosphere of the room reminds her of that of Mr. Shikamori's. As soon as he wakes up, he leaves for work without locking the door. It reminds her of Mr. Shikamori. She stays in the room until he comes back from work. She tells him to lock the door and goes home. The next day, he gives her a spare key so that she can get into his room whenever she likes. Eri receives the spare key even though she knows a spare key usually has some special meaning. Even though she told him he didn't have to give the money back, she's been waiting for his payday. On the payday, he gives her back the 200, 000 yen. Eri says to him, "Why don't we go to a coffee shop? I'll buy you coffee with this money." "Incredible. Let's go." says he.
In a coffee shop, he begins to speak.
Student: I told my boss that I was burgled because I didn't lock the door. Then my boss said one of the people who he worked with had never locked the door. He was an intelligent man and an excellent journalist, but he was so shocked when his loved one died and he ended up getting homeless. When my boss saw him, my boss thought he had made the whole world his own room and unlocked its door.
Eri: Who's your boss? What's his name?
Student: He is Mr. Yokoshima, a sales representative of P Corp.
Eri is sure Mr. Yokoshima spoke about Mr. Shikamori. She is very happy to know Mr. Shikamori is alive somewhere in the world. Eri meets Mr. Yokoshima.
Yokoshima: Yes, he is Shikamori. A nice guy. I saw him being homeless near the Tokyo station some ten years ago. He seemed to be happy. He said he didn't stay at the same place very long and that he wanted to go to as many places as possible. You probably will not be able to find him. But if you find him, please get in touch with me. I want to see him, too.
Eri walks around the town in the night. She walks in alleys, in the park, in front of the station looking at each person on the street. Her legs hurt when the dawn comes. Suddenly she feels the door of the whole world is gradually opening before her. She says to herself that she can play as she likes wherever in this world even if she gets muddy. Eri starts running holding the spare key in her pocket.