Green Corrosion by Costi Gurgu

After the ecological apocalypse brought by the Black Rain, liquid water turns gel and begins corroding people’s flesh. People consuming the gelled water suffer mutations. They are known as Corrosives, while those who still have access to liquid water remain the same, regular people. In the new world, they are called Liquid People.
GEORGE WOODMAN, the ambassador of the last liquid humans to the kingdom of a Corrosive leader, PRINCE BORIS, wants to save the kingdom’s people from the next Black Rain, but has to go against Prince’s political games and his people’s xenophobia. He is offered a Court guide in the person of princely concubine LADY L.
George falls victim to a trap set by the MAYOR of the capital city. The Mayor’s strongman, SILVER STAR, sends him home with a message—an ultimatum to surrender their clean water source to the Mayor.
Returning home he is again exposed to the political battle between his grandfather, WOODMAN THE ELDER, the CEO of the Woodman Corporation, and Councillor RUMI, his opponent for political power and fierce detractor of George and his work as an ambassador. Rumi sees the Corrosives as degenerates and wants nothing to do with them.
Although the Woodman Council decides to defend their water and withdraw the embassy, George runs away and makes a secret alliance with Prince Boris—he’ll become a Corrosive officer if Boris opposes the Mayor and defends the Woodmans.
George’s brother, ALEX, and his fiancé, BREE, follow George into the city. They plot to overthrow the Mayor and save George from becoming a Corrosive. The plot goes wrong and Alex dies. Bree goes into hiding and George is saved by Boris’ men.
Using George as the reason and the help of his infiltrated man, Silver Star, Prince Boris kills the Mayor and assumes control over the capital city.
George becomes a Corrosive, and discovers that behind the trap was Boris all along, setting up George, the Mayor and preparing for his coup d’état. George follows his secret plan to help the people despite being forbidden by the prince to do so. The secret city’s resistance against the power works with George in finding and securing a place that will protected them from the next Black Rain. George finds Bree and introduces her to the resistance.
Eventually, with the help of his spy, Lady L, Boris discovers George’s betrayal and George becomes from a top officer a hunted man.
Silver Star is sent to George’s home to conquer it. He succeeds in taking a small part of the Cave system that makes the Liquids’ settlement.
In the end, George saves the people and defeats Boris in a confrontation right before the Black Rain starts.