Ode to the Sword: Master and Apprentice (2016)

Seeking a great master in order to become a great Samurai, a young, naive Samurai is disappointed upon finding an honor-less, drunk geezer for a master. However, when the geezer saves him from a group of half-demons, the young Samurai realizes his mistake of judging the geezer's qualities by his appearance, and accepts him as his master.