Oretachi wa Koko de Koi wo Suru

Mizuo, your average modern day teenager, is mysteriously transported into Feudal Japan and worshipped as a Living Buddha in a time when war is the way of life-so it's no wonder he's desperate to return home! But Mizuo soon meets the charismatic leader of the Yamako army, Takakage, whose bravado on the battlefield is matched only by his adoration of Mizuo! When Takakage demands that Mizuo stay and become his personal page, will Mizuo still desire to return home?

(Source: Juné Manga)