Senbonzakura

Taisho Year 100. After the old capital, Tokyo's destruction in the Great Taisho Disaster, the seasons pass and a new capital, Oukyou makes a miraculous recovery centered around the holy cherry tree known as "Senbonzakura." However, following the Disaster, dark and evil paranormal events grow more common and the Kami-Tsuki Special Sakura Platoon take a stand to protect peace in the capital! Meanwhile, on a spring day, Miku has come to view cherry blossoms with her family. When searching for her older sister, she gets lost herself and comes across a gigantic cherry tree! Suddenly Miku finds herself wearing military clothes and under attack by a ninja! And then she's rescued by the twins Rin and Len, who call themselves members of the Kami-Tsuki Special Sakura Platoon...?

(Source: Kadokawa, edited)