Gensou Suikoden II - Hiki Sakareshi Shukusei

The Highland and the City-State have signed a peace treaty ending their war, but one night, on the camp of Highland's army of young men called the Unicorn Brigade, a massacre occurred, with only Tao and Jowy as the only survivors. They discover that the one behind this was the Highland prince, Luca Blight, and now, they were branded traitors of their own country... (Source: Manga Updates)