HYOUMA NO HATA: REVOLUTIONARY WARS

The story centers around Hyouma Utsugi, a son of a shogunate vassal family who received French-style military training to become an officer. In the middle of 1868's pivotal Battle of Toba-Fushimi, he encounters Shinpachirou Murata, a warrior in the opposing Satsuma faction who Hyouma once knew from his time studying abroad. (Source: Anime News Network) — Description from AniList community (anilist.co).