A farmer's daughter, aged 16. For unknown reasons, she already had been running away from home prior to being cryonically frozen. How the 7 Seeds organization got its hands on the young girl, is also still a mystery.
Because of that, in the beginning she doesn't care about involuntarily being thrown into the New World - until she realizes that her home really doesn't even exist anymore.
Matsuri's first appearance was in the fifth chapter of the series, "The First Day", on page 15. At first, she didn't play much of a role, only vehemently supported Chimaki when he was mourning silently at Kumamoto Castle. When Arashi, Semimaru and Natsu travelled towards Tokyo, the young woman stayed behind with the others to help out in creating a field.
Later on when everyone else in her group got caught up in a hole being completely unable to move, it was her time to shine. She provided her teammates with water through a shallow bamboo pipe and ran around to look for help. Thanks to her determination which made her even swim through a dark ocean at night, her comrades could be saved.
Afterwards, she continued her travels with the reunited Team Summer B until they crossed paths with the two outcasts of Team Summer A. It also was Matsuri who involuntarily triggered the first contact with them: Ango and Ryou felt obligated to save her when she had a dangerous accident during her tobogganing. She squealed in joy at the thought of being saved by two "handsome princes" and introduced the two of them to her group right away.
During the group's adventures on the Fuji ghost ship, Matsuri kept close to Ryou and gave him much food for thought...