In her teenage years, Yu Yu once encountered a bizarre kidnapping case.
The leader of the kidnapping was unknown, and the people involved were unknown. He was even unscathed and was sent home safely after being held for three full days.
Eight years later, Yu Yu, as a member of the "Black Algae" investigation team, participated in the investigation of the bizarre and terrifying domestic murder case of liquor corpses.
Yu Yu is a talented student, smart, careful, gentle and beautiful, but unfortunately he just doesn't know how to deal with the world. In "Black Seaweed", Yu Yu got acquainted with Qi Meng, a stubborn kid from the tsundere family with high IQ, psychiatrist Lan Xuan, and the mysterious and eccentric professor Lin.
Faced with Qi Meng, who has been in love for a long time, Lin who has been close to him many times, and various unexpected cases that come out of the blue.
How will Yuyu face it? Case after case is solved, and it seems that the leader of the deliberate kidnapping case in childhood has gradually unveiled his own veil...
This is "black algae", and above the city is the ink-stained sky.