Tensei shitara Zense no Otoko Tomodachi ni Kyuukon Saremashita  

転生したら前世の男友達に求婚されました, After reincarnating, I was proposed to by a male friend from my previous life

Two close friends who fought together during the Warring States period were separated when one of them died on the battlefield. They made a promise to reunite in another life, which eventually happened in modern-day Japan. Now, as a man and woman, they will likely have complex emotions upon their reunion.