How do you get the feirce deity mask no bosses deafeated?

To obtain the Fierce Deity Mask in "The Legend of Zelda: Majora's Mask" without defeating any bosses, you can use the "Goddess's Mask" glitch. First, go to the Moon and enter the area with the four giant masks. Use the "Song of Soaring" to return to the area where you can interact with the mask transformation. By manipulating the game mechanics, you can acquire the Fierce Deity Mask without having defeated any bosses. However, this method requires precise timing and knowledge of the game's glitches.