King of Tokyo has one of the most poorly written rules.
The rules state:
If a Monster loses its last life({Heart}) it is out of the game.
If you are attacked while in Tokyo and you don't want to be there anymore [...] you can yield to the Monster that attacked (he has to take your place). You still take the damage, however.
If you are eliminated by an attack on Tokyo, the Monster who attacked you automatically takes control of Tokyo.
Yielding Tokyo / Flee: A Monster can leave Tokyo (yield his place) to the Monster who just attacked him. If a card allows a monster to leave tokyo with no damage from an attack, the attacker still occupies Tokyo.
Eliminated: When you have 0{Heart}.
Does a Monster need to survive an attack to yield Tokyo?
This is important for a card like:
(5) Burrowing: Keep; Deal 1 extra damage on Tokyo.
Deal 1 damage when yielding Tokyo to the monster taking it.
Does a Monster eliminated by an attack deal 1 damage to the Monster that attacked them?