Majora's Mask 3DS - Deku Sword
- Mask Storage
- Deku Mask
- Ocarina of Time
- Call Epona with the Ocarina
- Perform Mask Storage
- Hold L and R and mount Epona.
- Unequip the Deku mask by dragging it back to the mask screen.
- Press "A" twice to dismount epona.
You should now be able to use the Sword on "B" after transforming.
To get your sword back, repeat this process with Goron Link.