Together, the two men took advantage of an intellectually disabled woman.
First, a man, who asked her to become his girlfriend the day he chatted her up on WhatsApp, pestered her to send a topless photograph of herself - which she reluctantly did.
He then sent the racy photograph to his friend and got him to upload it on Facebook.
Shocked and humiliated when she found out, she made a police report.
Yesterday, Gabriel Mok Shao Jie, 22, pleaded guilty to one charge of transmitting an obscene object by uploading it on Facebook.
The girl's "boyfriend", Samuel Koh Kwok Lun, 22, was earlier jailed 10 weeks, and is appealing his sentence.
Court papers said that on Feb 3 last year, the victim, 26, who cannot be named due to a gag order, received and accepted a Facebook friend request from Koh, then a full-time national serviceman.
A medical report stated that her intellectual development was within the mentally retarded range. They then began texting each other via messaging service WhatsApp.
After chatting for some time, the woman, who was working as a fast-food restaurant assistant, agreed to be Koh's girlfriend that very day.
A short while later, Koh told her he was feeling aroused and pestered her for a nude photograph of herself.
While initially reluctant, she eventually gave in and sent him a topless photograph.
Koh then sent it to Mok, who was then also serving his national service, and instructed him to upload it on Facebook.
Mok did so that evening using his Facebook account - which bore the moniker Gabriel Ong - with an insulting caption.
The girl's brother later saw the photograph on Facebook. By then, several users had seen and commented on it. He then told his sister.
At the brother's insistence, Koh asked Mok to take down the photograph, which he did. The woman made a police report the next day.
Mok is expected to be back in court on Oct 24 for sentencing while Koh's appeal will be heard on Oct 14.
The maximum punishment for transmitting an obscene object by electronic means is three months' jail with fine.