The Backspace and Delete keys remove the last character (JaMo) of the current syllable. The following procedure demonstrates how to delete characters of a syllable with the Backspace key.
Notice that the text you are composing appears highlighted in the preedit area.
To remove the last character of the last syllable, press the Backspace key once.
Notice that the last character of the syllable changes.
Press the Backspace key a second time.
The last character changes again.
Press the Backspace key a third time.
Notice that only the first character of the syllable remains.
Press the Backspace key twice more.
You have now removed each character in the syllable.