The slang lawyer Big Mouse is the head of the room.

The 12th episode of "Black Lawyer" finally revealed that the big mouse is the house chief. After meeting Chang Hao, the room chief admitted that he was a big rat. He could help Chang Hao build everything, but he asked him to attack the mastermind behind the paper. Later, Changhao proposed to Big Mouse that he should be superior to Big Mouse and that after catching Big Mouse, he would be his defense lawyer. "Black Talk Lawyer" plot synopsis:

A premeditated murder case turned third-rate lawyer "Big Mouth" Park Chang-ho (played by Lee Jong-suk) into a genius fraudster "Big Mouse" overnight, and was falsely accused of being trapped in prison. However, he was suppressed and bullied by various forces in prison, so he turned into a prison boss, making everyone think that he was a real "big rat", fighting evil with evil and fighting against the dark forces. In order to save her husband, his wife Gao Meili (played by Lin Yuner) cooperates with him to investigate the case. The couple vows to reveal the mastermind behind the scenes.