Bloodstained: Ritual of the Night

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Fast travel to Dian Cecht Cathedral. 2nd room directly to your left.

A very simple achievement, if you know where to find this location. Firstly, you will need the location Dian Cécht Cathedral unlocked. If you have found the fast travel room in it, from there, just go directly to your left, above the demon and continue straight until you enter another room. Then, just get your haircut!