The Warlord's Bride and the Shadow Ninja

Hikaru Kimura, a modern college student, falls into a river during an accident and wakes up in the Sengoku era — Japan's brutal age of warring states. She's quickly discovered by soldiers and brought before Inaba Kagetora, a warlord feared as the 'Demon General.' He's cold, ruthless, and oddly fascinated by Hikaru's strange knowledge. Without asking permission, he declares she'll stay in his castle as a concubine. Hikaru is terrified — but she has no power to refuse. Life in the castle is hard