Tsuki wa Yamiyo ni Kakuru ga Gotoku

Overview

The rumor goes that sometimes, late at night, a white monster appears, and if you should look upon it you'll be devoured. One night, Tetsu happens to glimpse the man behind the monster, and decides that the man would be the one to teach him the sword and allow him to take his revenge. However, the swordmaster Shino is hardly interested in taking on any students. What will Tetsu have to do to get his revenge, and what happened to Shino in the past to turn him into who he is...? Included one-shot: Volume 1: Holland Castilla Japanese Ka (阿蘭陀カステラジャパネスカ, Castilla)

Source: AniList