The micro-blogging service Twitter is an effective PR instrument, but one fraught with risk for celebrities who want to juice their notoriety by connecting directly and on their own terms with the public. Forgoing the filtering function of publicists, they may endear themselves to fans even more powerfully; or they may end up with feet in mouths and eggs on faces. You can do a lot of damage in 140 characters.

In this regard, TV personality Miyoko Omomo’s now famous tweet of Dec. 19 was considered reckless at first. Omomo had recently discovered that her ex-husband, journalist Toru Yamaji, had had an affair with another 40-something TV personality, Kuniko Asagi, while Omomo and Yamaji were still married. It didn’t matter that the couple divorced in 2006 because, as Omomo eventually revealed, she was never completely sure why Yamaji asked for a divorce in the first place. Four years later she found out and was so angry she announced the infidelity retroactively on her Twitter account while on her way to Narita Airport to catch an overseas flight.

The response was instantaneous. TV “wide shows” (current affairs variety programs) and tabloids picked up the story the next day, and since Omomo was unavailable they turned their attention to Asagi. As it happens, she is a regular commentator on the TBS show “Hiruobi” but understandably didn’t turn up for a few days. When she next appeared in public it was one of those standing press conferences that seem neither planned nor spur-of-the-moment. She tried to explain the situation while her lawyer, Junichiro Hironaka (whose clients also include political honcho Ichiro Ozawa), lingered behind her.

Asagi admitted that she had been “dating” Yamaji when he was still married to Omomo, but said Yamaji told her the marriage was hatan (broken) at the time, which she took to mean “over.” Hironaka said that the Supreme Court recognizes that when a marriage is hatan then any love affair a party undertakes is not considered furin (infidelity). In any case, Asagi admitted that she’d ended the relationship due to financial and emotional exhaustion.

The press was hardly satisfied with this explanation and soon learned that when Asagi said she was out of the relationship, she meant legally: She and Yamaji had married shortly after Yamaji divorced Omomo and then themselves got divorced this past November. Moreover, the affair had been going on for several years when they wed, which means that Yamaji was not only cheating on Omomo at the time, but that Asagi was cheating on her previous husband, musician Akihiko Matsumoto, whom she divorced in March 2006.

Even Asagi’s “Hiruobi” colleagues were surprised, saying on the air they were never aware she had remarried. Stung by accusations that she was being less than upfront, Asagi sent a fax to the press stating that she “didn’t mean to lie” and admitted that she and Yamaji were married for four years.

When she said the relationship had strained her financially, it was because she was supporting Yamaji and paying his rent. This revelation spurred further press speculation, which concluded that the couple never lived together and that one of the reasons Hironaka is hanging around is that Asagi still wants Yamaji to pay her back the money he owes her.

So who is this guy the ladies can’t resist? Yamaji is the president of news agency Asia Press Front, which he founded in 1992. APF dispatches reports from throughout Asia, the most prominent of which recently came from Myanmar. Kenji Nagai, the video journalist killed by government security forces during civil unrest in Yangon in 2007, was working for APF when he died. He was Yamaji’s mentor.

Yamaji himself was detained last fall by Myanmarese authorities. In fact, it was news of the detention that triggered the scandal. When media reported that Yamaji was arrested, they used the name on his passport, which wasn’t Yamaji but rather Matsumoto. Only a few reports explained this discrepancy, that Yamaji had married and taken his wife’s name, without saying who the wife was. Few people knew Asagi by her married name. Omomo, intrigued that her ex-husband had remarried without her knowing it, did some digging and directly called Asagi, who confessed to the affair. That’s when Omomo erupted with her fateful tweet.

Yamaji eventually came out and apologized for the subterfuge, saying that what he was mainly guilty of was zankoku-na chinmoku (cruel silence) toward Omomo. As for the affair, he opted for the Woody Allen defense: “Love is not a rational thing,” he said philosophically.

Show biz reporters have concluded that the reason he took Asagi’s name but didn’t live with her was so as not to distress Asagi’s 16-year-old daughter by Akihiko Matsumoto, but one journalist also advanced the theory that Yamaji took the name Matsumoto because it would make entrance into Myanmar easier, since immigration officials had flagged the name “Yamaji.”

Beyond accusations of conjugal dishonesty, Yamaji’s penchant for over-explaining his faults has drawn derision from media pundits. “I don’t know if he’s a good journalist,” said media gadfly Terry Ito on Nihon TV, “but as a man he’s pretty indiscreet.”

Nevertheless, Ito admitted that Yamaji seems to have a “talent” for seducing “intelligent women,” though the seduction may have been in the opposite direction. Both Asagi and Omomo belong to that subset of female TV personalities labeled “interi” (intelligent), an image they have cultivated assiduously, though Asagi has been more successful at it. She is currently a regular on seven programs, mainly quiz shows, while Omomo seems hard up for work at the moment, which may explain the tweet. She managed to put a professional rival on the media hotseat and in the process generate public sympathy for herself, but in terms of meaningful self-promotion its lasting effectiveness remains to be seen. These days you have to be a lot more reckless to keep people’s attention.

Phillip Brasor blogs at philipbrasor.com.