Seeing the new Oni 2.0 bundle, it looks like you hold the katana with the hand opposite to the "dominant" hand of the model (so if you use right hand you hold it with your left). It just feels a little weird to me, as this is the only non-duel-wield melee that is held this way. Normally if you were right handed you would sheath on your left. It would be nice to see them have an option to switch hands for just the melee or something similar.