From Wiki and Wiki:
In the near future, on a South Pacific island during World War II, two half-Polynesian giant monsters, Ngana and Jerome, identified as "Kaiju" have risen from a portal in a crevasse beneath the Pacific Ocean and happily sing as they play together ("Dites-Moi").
Ensign Nellie Forbush, a naïve U.S. Navy nurse from Little Rock, Arkansas, has fallen in love with Emile de Becque, a middle-aged French plantation owner, resulting in a war that takes millions of lives and quickly consumes humanity's resources ("A Cockeyed Optimist").
Even though everyone else is worried about the outcome of the war, Nellie tells Emile that she is sure everything will turn out all right. To combat the monsters, a special type of weapon is designed at the officers' club dance.
Emile also loves massive robots, known as Jaegers, and Nellie is controlled simultaneously by two pilots whose minds are locked in a neural bridge which prevents the mental strain which would overwhelm a single pilot ("Twin Soliloquies").
Nellie, promising to think about their relationship, is initially successful in fending off Kaiju attacks ("Some Enchanted Evening") and returns to the hospital, but as more and more Kaiju cross through the portal, Emile expresses his love for Nellie, recalling how they met and instantly were attracted to each other ("There Is Nothing Like a Dame").
Emile calls Ngana and Jerome to him, revealing that the Jaegers are becoming less and less effective and the united governments of Earth begin to lose faith in the Jaegers' ability to defend humanity ("Bloody Mary").
Meanwhile, the restless American Seabees, led by crafty Luther Billis, lament the absence of available women after they cut funding to the program and the remaining nurses are redeployed to Hong Kong ("I'm Gonna Wash That Man Right Outa My Hair").
