Sabiiro no Armor: Reimei

After many years of conflict, with the Muromachi shogunate growing ever weaker, Japan has entered the bloody epoch known as the Sengoku period. In the land of Ki, a place hidden by the sea and the mountains, there is a gun-toting armed force whose emblem is the Yatagarasu crow. This group, known as the Saika, earn their living as mercenaries on the battlefield. Their current leader, having inherited the traditional name of their commander, is a drifter from a foreign land known as Magoichi. Meanwhile, anticipating a threat from European powers, a man named Saburo makes plans to defend Japan. Magoichi and Saburo, whose fates could not be more different, will be forced together to face the foreign invaders. It's the beginning of a story about righteous, dashing men who live by their own ideals during an age of war! (Crunchyroll)