Oam Monogatari: Sono Natsu, Watashi ga Shitta koto
English name: The Tale of Oan: What I Learned That Summer
Type: ONA, Episodes: 1
Aired: Apr 8, 2018
Source: Book
Rating: G - All Ages
Synopsis:
A tourism promotion anime for Ogaki City in the Gifu Prefecture. It is based on Oam Monogatari, a book about a woman who spent her coming-of-age during the Sengoku Era. Oam is the main character and is the daughter of Yamada Kyoreki who is a vassal to the warlord Ishida Mitsunari. It offered one of the few historical viewpoints of an noble teen/woman's life during the wars. 

The anime jumps between past the present as we learn about Oam's struggles at Ogaki Castle (which would become ground zero for Battle of Sekigahara which established Tokugawa as the shogunate), and how Oam escaped with her mother in the dead of night.