Erasure

From The World Ends With You - Wiki on Neoseeker

Erasure is what happens when either a player or Noise is defeated in Underground. To be erased is akin to losing your life in the UG, and you remain dead in the Realground. When a player is defeated, his/her partner is also erased within 7 minutes. Although Beat was able to avoid erasure after his partner was erased because of outside help. The reason is because without a partner, it is hard for any player to survive because they cannot defeat Noise on their own. The rules of the UG also state that a player has 7 minutes of life after Partner erasure.