There’s no way to clear your saved data on the game, so you have to try this method in order to do it. Please keep in mind that you are attempting this at your own risk, as this may damage your game cartridge.

First, head to the game’s options menu and change anything (so, for instance, change damage from 1 to 3). Next, exit twice to get out of the menu. Turn the power off immediately following the second exit. This will interrupt your saved data. When you turn the game back on, it will tell you your save file has been corrupted. This will effectively erase your old save, allowing you to start from the beginning.