Umi Matsuzaki (松崎 海 Matsuzaki Umi) is the female protagonist of the From Up on Poppy Hill film.
Umi has a bob with lightly swept bangs with braids and hazel eyes. She is seen in her school uniform including a blue skirt, white shirt and blue line with a red ribbons tied around her neck in a bow, which resembles her grade. Umi's causal wear consists of a light pink top with a hot pink skirt and sweater.
Umi is a 16-year-old girl living in Coquelicot Manor, in Yokohama, Japan. She also known as "the girl who raises flags," because she raises the same pair of signal flags every morning and takes them down every night. When Umi was just a child, her father, a captain, taught her how to raise signal flags and explained that the flags meant "safe voyages." After learning how to raise signal flags, she raised the flags every time her father left port and only took them down when her dad's ship moored at the harbor. However, her dad was killed in the Korean War, when his supply ship struck a mine. Although, she continued to raise the flags hoping her message would reach him. Also, she pays her respects to her father with fresh flowers and a glass of water every morning.
Apart from honoring her father, she cooks and cares for the family and boarders, doing most of the chores like washing, cleaning, cooking and shopping. Her mother is currently in America studying in the medical field. Eventually, Umi meets Shun, a boy whose a member of the school's journalism club remembering him from his daredevil stunt to save the Quartier Latin building. Their second meeting was when her younger sister, Sora, requests her to accompany her to the Quartier Latin building to ask for Shun's autograph. After Shun's stunt to save the Quartier Latin building, Umi has been rather aware of Shun's actions. The two become friends, after Umi helped him with the school's paper numerous times. After getting along with the members of the Quartier Latin building, Umi became known as the "goddess of goodluck" due to the fact that she was responsible for the idea of cleaning and repairing the building as an idea to save it from being demolished.
When Umi invites Shun to Miki's going away celebration, Umi shows Shun a precious photo of her father and two other men he went to school with. Shun's eyes stared at the photo, unable to speak. Shun eventually tells her about the possibility of them being siblings which greatly affected their relationship. Shun began to avoid Umi, but despite the possibility of them being siblings, he falls in love with her and they both confess their feelings for each other.
After the issue of Quartier Latin's demolition is resolved, Shun and Umi are summoned to the harbor by a man named Yoshio Onodera, the third man to the left in the photo both Umi and Shun have of their fathers (this photo was responsible for their beliefs that they could possibly be related) who is now a ship's captain. He confirms that Umi and Shun are not related by blood stating that Shun is indeed Tachibana's son and Umi is indeed Sawamura's.
- Hana Matsuzaki (grandmother)
- Ryoko Matsuzaki (mother)
- Yūichirō Sawamura (father)
- Sora Matsuzaki (younger sister)
- Riku Matsuzaki (younger brother)
- Shun Kazama (love interest)
After my dad was killed in the Korean War, that was that. But I never stopped raising those flags... I never missed a day.
- —Umi to Shun about the signal flags she that raises
- In the original manga her surname is Komatsuzaki (小松崎).