Patriot of the Sea - S1.E16

As Izumi and Sakamoto are out exploring they encounter a young boy named Soushi Okita. Okita challenges Izumi and Izumi decides to play along and try and lure Sakamoto into a duel. However, soon Okita's master a man named Hijikata Toshizou appears and Izumi recognises him as a strong opponent. The two exchange words and vow that when next they meet their true skills sill be revealed. Izumi also promises Okita that one day they will fight to the death. Having witnessed this Sakamoto is finally ready to fight with Izumi. However, durring the fight Sakamoto has a realisation that he want's to change the world not simply fight agains it. As such he vows to Izumi that he will never again draw his sword, and Izumi vows that he will always be there so that Sakamoto won't have to.