An Indonesian woman was tortured for three days with a belt and sex toys before her tormentor cut her throat, the High Court heard on Monday.
Jurors were also told how banker Rurik Jutting then filmed himself talking about the first killing before murdering another Indonesian woman by cutting her throat five days later.
On the first day of the Briton's trial, the prosecution gave detailed accounts of the deaths of Sumarti Ningsih and Seneng Mujiasih in 2014.
Jutting has denied two counts of murder but pleaded guilty to two counts of manslaughter.
Ningsih, 23, was said to have been in Hong Kong on a visitor's visa before she was killed.
Jutting asked her to spend time with him on October 25, 2014, the court heard. He
later subjected her to "increasingly cruel acts of violence using his belt, sex toys, a pair of pliers and his fists" in his Wan Chai flat, prosecutor John Reading told the court.
"After torturing her for three days he took her into the bathroom ... made her lick the toilet bowl, and then he cut her throat with a serrated-edged knife," the barrister said.
Ningsih did not die immediately, so Jutting dragged her into the shower and continued to "saw through" her neck until she was dead, the prosecutor continued.