The story is set in summer, 1943.
Two years ago, on December 8th morning, Tsuzumi heard the radio news say a war had just
begun. She thought everyone was going to be killed and cried.
Tsuzumi has realized she is unlikely to be killed because she lives in a faraway town from Tokyo. Tsuzumi lives with her step-mother, Asagi. Asagi is quirky, pretty, and so tall that everybody is surprised to see her. She's become even more strange recently. She cries alone every night, as if she was Kaguya-hime, who has to return to the moon. Tsuzumi's father died ten years ago and Tsuzumi doesn't think her mother cries for him.
One day Tsuzumi is picking flowers in the field to sooth her mother, when Momotarou calls her. Momotarou hands her a lot of vegetables and says his brother , Kentarou, wants to give them to Tsuzumi's mother. He says his brother sighs every night. Tsuzumi tells him her mother also sighs and cries every night. Momotarou says they must be in love with each other. Even though Momotarou says it's a good idea for Kentarou and Tsuzumi's mother to get married, Tsuzumi hesitates to agree with him. Momotarou insists that Tsuzumi should be happy to hear that because both Kentarou and Asagi have never had a love affair since they began to look after Momotarou or Tsuzumi alone. Momotarou invites Tsuzumi to come to their place the next day because it will be Kentarou's birthday.
Tsuzumi and Asagi have been very close even though Asagi is a step mother. Tsuzumi doesn't want Asagi to love or care about anyone but Tsuzumi. However, Tsuzumi thinks she should be independent from Asagi now that she is 13 years of age.
Coming home, Tsuzumi tells Asagi she has decided to allow Asagi to marry Kentarou.
Asagi: What are you talking about?
Tsuzumi: Remarriage isn't morally wrong.
Asagi: I love your father.
Tsuzumi: He's been dead for ten years. Do you cry every night for him?
Asagi: No. Not for him.
Tsuzumi: Then tell me why you cry every night.
Asagi: I can't say.
Tsuzumi: I know why. Kentarou sighs every night. He is also in love with you.
Momotarou invited us to Kentarou's birthday party. I'm not a baby. I want you to pursue your own happiness.
Asagi: Tsuzumi, if I get remarried, I won't be able to be always with you.
Tsuzumi: I know.
Asagi: You cried when I went out for shopping last week.
Tsuzumi: It won't happen again.
Asagi: I won't be able to accompany you when you go to the toilet in the night.
Tsuzumi: I'll try to go by myself if you and Kentarou decide to get married. So please go to his birthday party with me.
Asagi: Ok. I will.
Tsuzumi and Asagi go to Kentarou's place the next day. Momotarou tries to hear Asagi and Kentarou talk alone in Kentarou's room. "I'm 27 years old" says Kentarou, "You are a year older than me" says Asagi. That's all they talk. Momotarou is disappointed and invites Tsuzumi to go out together so that Kentarou and Asagi can talk more freely.
Kentarou: Then, you didn't get married officially.
Asagi: I was a wife of that kind.
Kentarou. You've said you and your late husband lived in nearby places but you didn't know each other. Tsuzumi's real mother died immediately after she gave birth to Tsuzumi. Your husband raised her until she became 3 years old. After he died, you arrived at the age of 16.
Asagi: It was on the seventh of July.
Kentarou: How could I call you his wife?
Asagi: I was always looking at him when both of us were students. I didn't change my mind even though he didn't look at me. I came to look after Tzuzumi because she was his daughter.
Momotarou and Tsuzumi are playing near the river. Tsuzumi has a memory about the river and Asagi. One night, she woke up to find her mother nowhere. Being surprised, she went out to look for her mother. When she arrived at the river, she found Asagi swimming in the river. Her long hair was floating after her. Under the moonlight, Asagi looked as if she was a mermaid or some unknown creature. "Mother!" cried Tsuzumi. Asagi looked surprised to hear that. She went into the shadow and told Tsuzumi not to see her until she got dressed. "If you look at me, I won't be able to be with you any more." said Asagi. Feeling scared and fun at the same time, Tsuzumi followed Asagi's words. Whenever she comes to the river, she recalls the memory and wonders what Asagi is. That could be why Tsuzumi fears that Asagi might be gone unless she always keeps an eye on her.
Tsuzumi slips in the river. Momotarou helps her stand up and his face comes very close to Tsuzumi's face. Tsuzumi can't think about anything but his face after coming back home.
When Asagi returns home, she says Kentorou is a delinquent. She says she slapped him because he held her down and kissed her.
Tsuzumi: Mother, have you forgotten the time when you and Father loved each other? Did you slap Father when he kissed you?
Asagi: We didn't kiss.
Tsuzumi: Don't be stupid.
Asagi: I'm not the same as others. To tell you the truth, I'm not a human. So I wasn't able to get married to your father even though I loved him very much. When your father died, I metamorphosed into a human to look after you.
Tsuzumi: Mother, I'm not young enough to believe such a fairy tale. Now I know why Kentarou kissed you. He is really in love with you. He got excited as I did today.
Asagi: As you did today? What did you do today? Tell me!
Tsuzumi: When Momotarou helped me stand up in the river, I felt like kissing him.
Asagi: Then? Did you and Momotarou kiss?
Tsuzumi: Yes, we did. So you too,…
Asagi runs out of the house to Kentarou's place to Kentarou's place with a laundry bamboo stick.
Momotarou appears and says Kentarou is out.
Asagi: It's you that I want to talk to.
She hits him with the bamboo stick. Tsuzumi runs after Asagi and shouts at her.
"Shut up, Tsuzumi" shouts back Asagi.
Asagi: How old are you?
Asagi: Will you become a doctor?
Asagi: I asked a question. A doctor doesn't fight at the front line and has more chance to survive than common soldiers. You'll be able to protect Tsuzumi if you can survive. Will you become a doctor?
Tsuzumi: Mother, I lied to you. Momotarou and I didn't kiss. I just wanted to kiss him. He isn't responsible for that at all.
Asagi: Momotarou, answer me!
Momotarou: I will become a doctor.
Momotarou almost passes out. Asagi throws water at him.
Asagi: Don't pass out. We'll have an engagement ceremony tomorrow. Do you agree?
Tsuzumi: You, stupid, Mother! That's not your business. I hate you!
Asagi: Can't you speak, Momotarou?
Momotarou: I will get engaged to Tsuzumi.
He passes out.
Tsuzumi: Momotarou, wake up! I hate you, Mother! I won't get engaged to him.
When Tsuzumi is sitting down outside her house, Momotarou comes. He says he has been in love with Tsuzumi since he was a child. He says he doesn't care if he was hit. However, he wants to know what Tsuzumi is thinking. He asks her to marry him. Tsuzumi accepts his propose.
Tsuzumi writes a letter to Asagi. "I won't sleep outside. I will get engaged to Momotarou tomorrow. I don't hate you. I won't hate you whatever happens. Please get along with Kentarou. I wish your happiness." Asagi recalls the time when Tsuzumi was very young. Tsuzumi was always crying. Asagi wondered why Tsuzumi was so sad. Asagi sometimes invited Tsuzumi to play tag to sooth her. Asagi remembers Tsuzumi stopped crying in the game and was looking at the sunshine through the leaves of trees.
After the engagement ceremony, Asagi tells Kentarou she has something to confess to him. Kentarou says he also has something to tell her and wants to tell before her. Asagi agrees with him because her confession might give Kentarou a heart attack.
Kentarou: I won't be surprised to hear anything. I have to go to the war. I received a letter yesterday after I was slapped by you. I appreciate you have settled things about Momotarou. I have to make an apology to you because it was too stupid that I thought I could make you happy. I'll leave here as soon as possible. I love you even though you dislike me.
Asagi: It's my turn.
Kentarou: I know what you want to say. I know you dislike me. If you are going to tell about yourself and if it's horrible for you to tell……
Asagi: I'm impressed with your personality like that. That's what both I and my late husband lack. I'll accept your love.
Kentarou: Will you accept my love?
Asagi: I will.
Kentarou: I promise I will come back alive from the war.
There is a banquet for celebrating the engagement and Kentarou's going to the war. Momotarou hears Kentarou is going to the war for the first time at the banquet. The next morning, Tzuzumi sees Asagi going out of Kentarou's bedroom.
On the day when Kentarou leaves his hometown for the war, Momotarou is crying. Tsuzumi soothes him. Momotarou stays at the guest room in Tsuzumi's place that night. Tsuzumi is too excited to fall asleep so soon but finally falls asleep and has a dream. In the dream, Asagi is swimming. Her long hair is floating after her. When Tsuzumi looks back at her, Asagi flies up in the air with a white outfit. Tsuzumi extends her arms and calls Asagi. Asagi looks as if she was in despair. Tsuzumi keeps calling Asagi and the white outfit goes further and further. "I've never seen anything, Come back, Mother!" cries Tsuzumi, and she wakes up. She has sweated and is very thirsty. She goes to the kitchen. There is a pot of water, which Asagi always places there. Tsuzumi's fear that Asagi isn't in her room makes her look into Asagi's bedroom. Asagi isn't there. There's no futon. "It's happened after all." thinks Tsuzumi. She goes outside barefoot.
She runs and runs toward the river. "Mother's leaving from the river, Mother, Mother, Mother!". When Tsuzumi arrives at the river, she isn't able to utter a word. The blue moon is shining and she sees the hair flowing in the river. It isn't Asagi's long hair but a lot of cut hair.
Then Tsuzumi sees Asagi's brows, nose, eyes and mouth in the face of a tall young man with a short hair, who is wearing a white linen shirt. He smiles at Tsuzumi and goes away. Tsuzumi can't move even though she thinks she had better go after him. Tears are dropping from her eyes.
When the dawn comes, Tsuzumi comes back home. She finds out her father's shirt, trousers, socks and shoes are gone. She finds two letters on the desk. One is from Asagi to Tsuzumi. Asagi says "Good bye" in it. Tsuzumi doesn't understand that until she's read it five or six times. The other is from Asagi's grandmother to Asagi.
It reads, " Dear grandson, it took more than ten years to find you. I saw you laughing. Your appearance is unbelievable to me. I don't know why you do that. However, I will do my best to help you. So please come back to us. Your father died. I have received a letter from the army. You have to go to the war. Please don't damage our family honor."
The letter is dated the day when Asagi began to cry in the night.
Later, people in the town talk about the missing woman and hair that were flowing in the river. They speculate she committed suicide. The war ends two years later. Momotarou continues to study for becoming a doctor. He and Tsuzumi end up getting married. Neither Kentarou nor Asagi comes back from the war.
The memory of that summer remains clear in Tsuzumi's mind. It seems as if the bright summer sunshine and the reflection of the water that can't be looked straight.