Manga Back Street Girls - Washira Idol Hajimemashita.

A group of 3 yakuza failed their boss for the last time. After messing up an important job, the boss gives them 2 choices: Honorably committing suicide, or go to Thailand to get a sex reassignment surgery in order to becomes "female" idols. After a gruesome year long training to become idols, they successfully debut, with overwhelming popularity, much to their dismay. This is where their tragedy truly begins.