The former F4 member revealed in April this year that he had patched up with ex-girlfriend Arissa. Marriage was on the cards during their reconciliation then.
The two used to date for a year in 2006, but broke up when the pair drifted apart when Arissa was studying in the US.
In a post dated September 4 on Twitter, the 31-year-old actor-singer hinted at his heartache and breakup with his squeeze.
"No [,] I'm not saaayin~ [that I'm] soooorrry~ One DAY! Maybe we'll meet again~~~Closer to the edge," wrote Vanness. A day earlier, he posted, "where it lies, is where you left it, where you left it, is where it died... revive, revive... revive the heart."
News of their breakup surfaced when eagle-eyed Taiwanese netizens discovered that the couple was no longer following each other on Twitter. Arissa also posted a picture on her Twitter, where she was seen posing with a guy - believed to be her new lover.
A devout Christian, Vanness has taken a chastity pledge against pre-marital sex.
However, his ex-girlfriend is widely known for her liberal ways like posing sexy pictures of herself online. Could a clash of "sexual interest" be the catalyst to the failed relationship?
Vanness's manager responded, "He feels that she is not a celebrity, and hopes for her privacy to be respected. It's not convenient for him to speak about such topics."
Arissa has also denied allegations that the breakup was due to a third party.
Vanness is currently busy with preparations for his upcoming album. He will be heading to France for the filming of his new drama, Material Queen, in October.
