The woman has been caught on closed-circuit television footage and earned the nickname in media reports for her pout.
The first cases attributed to the duck-mouthed girl apparently took place in October of last year when she struck up a conversation with a salaryman in his 40s in the Ebisu district of Tokyo.
The woman was wearing an imitation leopard-skin hat and reportedly told her victim that she was a voice actress.
After they ended up in a short-stay "love hotel" close to Meguro Station, the last thing the man remembers was having a drink.
When he woke up, the woman had gone while his wallet and expensive watch were missing.
In December, a real estate broker was similarly seduced by the same woman. After a brief stop in a 24-hour store to buy alcohol, they returned to his apartment in west Tokyo.
The Shukan Bunshun news magazine said the man had a drink that had apparently been spiked with sleeping pills.
When he woke up, the woman had made off with 57,000 yen (HK$4,300) in cash and a watch worth 500,000 yen. On Christmas Eve, another man was picked up in a noodle shop in Shibuya before he was later robbed of 300,000 yen.
Tokyo Metropolitan Police declined to comment on the case on the grounds that their investigation is ongoing, but have released an image of the woman taken in a convenience store.
They estimate that the duck-mouthed girl is around 155cm and seems to favour the leopard-print hat when she is seeking a new target.
They have played down suggestions on some web sites that the suspect is a transsexual.
Japanese media have noted that she bears a superficial resemblance to actress Aiko Ito.
In response to the authorities' appeals, several additional men have come forward to say they have fallen for an identical scam in the Ueno, Roppongi and Yotsuya districts of Tokyo.
Police now believe the actual number of victims is likely to be far larger.