by pillinjer
The rules say:If a Monster is eliminated and that brings the number of Monsters below 5, Tokyo Bay can't be occupied anymore. The Monster in it must leave Tokyo.
So, If P1 is in tokyo, P2 in Tokyo Bay and p3 Attacks and kills P1 taking the total number of players under 5, then p3 enters Tokyo, and p2 leaves Tokyo.
You cant move from Tokyo Bay to Tokyo at any time in the game it seems.