Mikage’s grandmother has just died, and Mikage is in a haze of grief, unable to sleep. Mikage’s mother and father died when Mikage was very young, so Mikage’s grandmother raised her. Now that her grandmother is dead, Mikage has nobody in the world and feels utterly alone in the dark universe. The only place Mikage can sleep is in the kitchen, which is where she’s been for days when Yuichi Tanabe knocks on her door. Yuichi goes to Mikage’s university but she doesn’t know him well, although Yuichi was close with Mikage’s grandmother. Yuichi suggests that Mikage come to stay with him and his mother Eriko for a while. Yuichi seems to glow with light and Mikage is compelled to accept the invitation.
When Mikage enters Yuichi’s apartment, she is drawn to the kitchen full of plates, pots, and pans, and sinks into the massive, soft sofa. Mikage is dazzled by Eriko’s beauty and amazed when Yuichi explains that “[Eriko] is a man.” Eriko was actually Yuichi’s biological father, but after Yuichi’s biological mother died of cancer when Yuichi was a baby, Eriko decided to become a woman, open a nightclub, and raise Yuichi as his mother. It seems perfectly natural to Yuichi to see Eriko as his mother as she’s so feminine. Mikage feels strangely comfortable in their apartment and agrees to stay, sleeping on the giant sofa in the kitchen, next to a window framing a dark sky dotted with stars. Mikage stays with Yuichi and Eriko for several months, falling into an easy rhythm of working part-time and tending to the house. She cooks for Eriko and Yuichi often and they enjoy sharing meals together. Eriko is very motherly towards Mikage, which warms Mikage’s heart.
One day, as Mikage is cleaning out her grandmother’s apartment, her ex-boyfriend, Sotaro, calls to check in. They meet for a friendly catch up, and Sotaro tells Mikage that Yuichi’s girlfriend slapped Yuichi in the cafeteria when she heard about Mikage living with Yuichi. Mikage laughs and explains that Yuichi and Eriko more or less adopted her and there’s no romance going on. Mikage dated Sotaro because she was drawn to his perpetually upbeat outlook, but now she feels more at home among the “strange cheerfulness” of the Tanabes. That night, Mikage tries to subtly broach the topic of the cafeteria incident with Yuichi but, to Mikage’s irritation, he’s completely dense and doesn’t pick up on her cues. Eventually, Mikage has to ask Yuichi about it directly and he smiles bitterly, saying it couldn’t be helped. Mikage can tell Yuichi is touched by her concern and they warm to each other in a different way.
Soon after, Mikage goes to her grandmother’s apartment to finish cleaning it out. It’s dark and chilly as she catches the bus home. On the bus, she watches a grandmother soothe her grandchild. Mikage gets off the bus and sobs violently, crying for the first time over her grandmother’s death. That night, Mikage sleeps soundly. Mikage wakes in the middle of the night after having a strange dream about cleaning her grandmother’s kitchen with Yuichi and singing a song with Yuichi about a lighthouse in the dark ocean. Yuichi is also awake and is hungry for ramen—which he also asked for in his dream. They are both shocked to realize they had the same dream. Mikage feels as if they are standing in a brightly lit room that pierces the vast darkness of the world around them.
One day, Eriko is gracefully watering the plants and telling Mikage about the time when Yuichi’s biological mother died. Eriko tells Mikage that life can be very hard, but those who never suffer can never understand joy. Mikage is comforted by Eriko’s words and thinks to herself that she’ll experience many moments of pain in her life but knows that she’ll keep going and won’t let her spirit be broken.
That autumn, Eriko is murdered by a stalker who couldn’t get over the fact that he was attracted to a transgender woman. He attacked Eriko one night with a knife, and, in her dying moments, Eriko beat him to death with a barbell. Mikage doesn’t find out until several months later, when Yuichi is finally able to call and break the news. Mikage feels blank and disoriented but hurriedly packs an overnight bag and rushes to Yuichi’s place, feeling like she can’t see or breathe. Yuichi is thin, downtrodden, and terrified that Mikage is angry at him for taking so long to call, but Mikage dismisses the thought.
That night, Mikage reads Eriko’s will. Even in death, Eriko is empowered. Her will is a cheerful letter assuring Yuichi that if she’s dead now, he should remember that she was—in body and soul—a beautiful woman and mother who loved her life, no matter what end she met. Eriko also writes that she thinks of Mikage like a daughter. Mikage misses Eriko so much that she feels she’ll go mad and cries herself to sleep.
The next day, she offers to cook a feast for Yuichi to cheer him up. Yuichi is enlivened by the idea and rushes out to get the ingredients. Suddenly, Mikage feels heavy as visions of Eriko’s face torment her. Not knowing what to do, Mikage starts to clean the kitchen. As she cleans, she starts to feel better.
Yuichi’s excited to eat Mikage’s food because she’s a professional now. Mikage became obsessed with cooking over the summer when living with Eriko and Yuichi, and poured her heart and soul into it, feeling utterly blissful. She now works for a famous cooking teacher. Mikage feels that although the students in the cooking school seem happy in their comfortable lives, their happiness falls short of her own joy. Mikage cooks with a profound joy that she can only appreciate because of the suffering she’s experienced.
That night, Yuichi drunkenly asks Mikage to stay for a while, and she asks him to explain if he needs her as a friend or a lover. Yuichi becomes despondent, saying he can’t think straight. Mikage discovers that Yuichi has been drinking himself to sleep every night and is in a dark place. Mikage imagines her and Yuichi climbing down a ladder to hell and realizes they can’t create a life together in this place of pain.
The next morning, Mikage rushes to work, not knowing what to do about Yuichi. Luckily, Mikage’s boss says she needs Mikage to come on a work trip to the Izu Peninsula. Mikage jumps at the chance to get some distance and perspective. While Mikage is chopping vegetables at work with her colleagues Kuri and Nori, a girl named Okuno storms in. Okuno accuses Mikage of leading Yuichi on and emasculating him, before storming out. That evening, Mikage feels drawn to Yuichi while they go out for tea. She buries her head into Yuichi’s arm as he walks her home and he says they’ll go for tea again when Mikage is back from her trip. That night, as Mikage is packing, Eriko’s dramatic friend Chika calls with urgent news for Mikage. When they meet, Chika explains that Yuichi came to the club feeling lost and alone. Chika says she knows Yuichi and Mikage are in love and gives Mikage the address of the inn she sent Yuichi to, urging Mikage to chase her lover.
It's evening at the Izu Peninsula and Mikage walks around town looking for food. She walks into a brightly lit cafeteria and orders fried pork. Impulsively, she calls Yuichi, who sounds faraway. He jokes that there’s no food where he is except tofu. Suddenly, Mikage has an intuition that her and Yuichi are negotiating a turning point and things could go either way for their relationship. Yuichi lies that he’s coming back soon and they say goodbye. Mikage feels exhausted. The pork is served and it’s mind-blowingly delicious. Mikage inhales it and it brings her back to life. Suddenly, she’s seized by an impulse and grabs another order to go. Before she can think about it, she’s in a taxi headed far away to Yuichi’s inn.
Yuichi’s inn is locked up tight and nobody is answering the phone. Mikage decides to scale the wall and somehow manages to haul herself onto the roof. As she lies in a puddle, clutching the pork and her arm (which is now bleeding), Mikage stares up at the moon with a profound sensation that she was destined to wind up in this predicament.
Mikage knocks on Yuichi’s window and he is shocked to see her standing there with takeout food and a bleeding arm. Yuichi’s eyes look cold and Mikage is suddenly frightened, feeling like she’s trapped in Yuichi’s pain. Mikage confronts Yuichi about running away to start a new life and tells him to eat the pork first, which he guiltily takes. As Yuichi opens the container, happy memories of Mikage’s good times with Eriko and Yuichi come flooding back to Mikage like a dazzling crystal. Mikage is no longer afraid. Mikage tells Yuichi that she doesn’t want to lose him. Yuichi, who has been devouring the delicious pork, looks Mikage in the eye. He explains that he was running away because he didn’t want Mikage to see him in his weak and unmanly state. Mikage thinks he’s being ridiculous and cracks a joke about Yuichi tearing a telephone book in half to reclaim his manliness. Yuichi is enlivened and they joke about increasingly absurd shows of manliness. Glad to see some light coming back into Yuichi’s face, Mikage leaves him to think about what she said and they goodbye.
Back in Izu, Mikage walks along the icy beach at night, looking at the dark waves. A lighthouse in the distance casts its beam of light towards Mikage and she makes peace with all the pain and joy that is yet to come. When Mikage gets back to the inn, Yuichi calls. They joke a little and Yuichi says he’ll pick up Mikage at the station when she gets back to Tokyo tomorrow.