Sangokuden no Gaim

After stopping a thief in the museum with his two friends, Yamato Kusanagi found himself in a new world, where the major figures of the Three Kingdoms era are all beautiful girls. With his companions on his side and as the new Gaim, he seeks to unite the land bringing peace to ancient China and stopping Helheim Forest to Devour this world. Just Live More! Rated M just in case.