Before they shot the movie, four actresses spent a day at the house together to get familiarized with the layout of the house and get comfortable with each other. They cleaned the house, weeded the garden, cooked meals and ate together. They also fixed the shoji screen, which Koreeda liked it so much that he incorporated the scene in the movie.
When Koereda first read the manga series "Umi-machi Diary", he was immediately attracted to the story which dealt with family, death and child being abandoned and felt he was the right director to bring it to film. He contacted the author but found someone already had a right to the book. Couple years later he was informed the right to the book had been withdrawn and it was his if he was still interested.
Koreeda felt the house was a central part of the story. After extensive search, they found the house in Kita Kamakura. They were just going to use only the gate and out side of the house. But when they saw front entrance, yard and rest of the house, Koreeda felt sets wouldn't reflect the reality and soul of the house. They asked the owner of the house for permission to use the entire house including everything in the house as they are. Only set they recreated was the kitchen when Sachi and Yoshino cooking noodles. The owner even gave them a permission to mark the wooden post Sachi marked Suzu's height.
Suzu Hirose, who plays Suzu, had played basketball in junior high but had never played soccer. For character, Suzu, playing soccer was major part of her life. It made her feel alive, accepted, enable for her to make friends and have her own "ibashiro (a place you belong)", and be a "child". Koreeda felt it was important that Suzu played soccer well enough to put it on screen. She, along with Ohshiro Maeda, who played Futa, was assigned a soccer coach and took up soccer training close to a year. She became quite an able player many in media thought Suzu had been playing soccer for a long time. The goal scene was reshot many times, even after Koreeda was satisfied, until Suzu felt it was good enough to make spectators' cheer believable.
Koreeda's Non-Script: In previous movies he made, he did not give script to child actors. He just mouthed the dialogue to child actors as the scene took place and the child actors repeated what Koreeda had just said, reacting to what other actors were saying and doing at that moment. It made it easier for child actor not having to memorize dialogues and helped them act more naturally. Since Suzu was not exactly a child, Koreeda gave she her a choice of either to have a script or not have one. She chose not to have a script, thinking this might be the last chance she would be able to act this way.
They started the shot in April 2 (first day of new school year scene) and ended on December 24 (The window scene where four sisters look out from the Suzu's window and talked about plums after plum-wine incident.)
Japanese title for Our Little Sister is called "Umi-machi Diary(Sea-town Diary)" based on manga series by Akimi Yoshida with the same title. There are seven volumes and Volume 8 on the way. There is a novella called "Umi-machi Diary" which is based on the film. Also a photography book "Umi-machi" Diary" by Mikita Takimoto, cinematographer of the film - a collection of photographs he took during the filming. They were originally intended for promotion but both Korea and Takimoto liked the photos so much they decided to publish them as a book. There also is a magazine called SWITCH and May 2015(Volume 33 No.6) edition has extensive coverage on "Umi-machi Diary" and Koreeda. Unfortunately, they are all in Japanese.
Haruka Ayase, who played the eldest daughter Sachi, is know in Japan for her open, bubbly and sunny personality who is quick to laugh. When Koreeda met her, he came away with an impression that Ayase was more of a "Woman of Showa Period (1926 to 1989)" and close to Oz's muse, Setsuko Hara with her quiet and introspective beauty, elegance and grace. With this in mind, he wanted to shoot the film in style after Ozu. During the filming of dining scene when sisters discussed their father's death, he positioned the dining table in a manner Ozu had used - having the table set perpendicular to the line of tatami mattress. However, Koreeda felt the perpendicular composition to be too formal and restrictive. So he decided to move dining table and actresses around a little off horizontal to make the scene more natural and every-day family life-like, ended up much closer to what Director Naruse did with his composition.
UK version of DVD and Blue Ray does not come with Behind the Scene and other extra. There is a Japanese Special Blue Ray version with no subtitle which has 'The Behind the Scene', 'Four Sisters revisiting places from the movie in Kamakura', 'Cooking food from the movie', 'Cannes Film Festival' (where Koreeda looked like a proud father of these four sisters) and couple others. You can see how the movie was made, Koreeda's thought process and what four actresses are really like in person. Haruka Ayase who played Sachi will surprise you.