These hooks hold my wooden katana on the wall. Use 8x3 mm 

(the top of the screwhead should be 8mm and the shaft of the screw should be 3mm) countersunk screws (any length is fine) to mount it to the wall. They are a fairly specific size so they may not fit your katana or anything else you may want to mount on the wall. If they do then great but if not you can use this as a template. I uploaded a some measurement so you can check the fit. For the files I have uploaded a .3mf as well as a .stl for whichever you prefer as well as a .f3d file so you can easily edit it in fusion 360. Print with 15% infill, any layer height should be fine, no supports and you may want a brim or raft depending on the amount of warping you get.