Complete Story mode as Sanada Yukimura, and unlock Fuma Kotaro. Play through and complete Fuma Kotaro's story. Finally, complete Fuma Kotaro's Story for a second time however this time follow a specific order in your battles:

Battle 1: Noshima (Tsuruhime)
Battle 2: Nakatomigawa (Motochika)
Battle 3: Osaka (Mitsunari)
Final Battle: Mikatagahara (Ieyasu)

Afterward Hottari Hanzo will be unlocked as a support Character (Ally). His ability is a 2x chance to find fugitives. When Hattari is at maximum level the fugitive will be marked on the map.