On the Taiwanese portal Pixnet, which features many celebrity blogs, they also managed to beat girl band S.H.E and rock band Mayday in terms of daily hit rates.
Fans have raved about their hip-hop dancing video clips and their cute, earnestpostings about daily life and trainingin Taiwan.
One response on their Pixnet blog even offered the girls a showbiz contract.
Sorry, guys, By2 has been signed by Singapore's Ocean Butterflies Music, which had groomed local singers JJ Lin and A-do to regional fame.
The girls were discovered two years ago at the Extraordinary Singer's Course organised by Ocean Butterflies' subsidiary school, Music Forest.
After beating rivals at talent quests organised by Ocean Butterflies, they were offered a 10-year recording contract, said their mentor, Mr Billy Koh.
Mr Koh, the acid-tongued judge of TV talent quest Project Superstar, said the girls would release their debut Mandarin album by June.
He added that they would also play a minor role in a new McDonald's TV commercial starring JJ and also guest-star in a Pepsi-sponsored movie named Kung Fu Pop.
Mr Koh is counting on By2's upcoming debut to 'rewrite history' in Singapore.
'No singer from Singapore has started out so young and managed to conquer the entire Chinese pop market,' he told The New Paper over the phone from Ocean Butterflies's overseas branch in Beijing.
He stressed that he's not suggesting that 'everybody should quit school' to be pop stars.
He said he just hopes that By2 can crack the 'rigid thinking' of Singaporeans who feel that the right passage of life is to study hard, get a good degree and get a stable government job.
'We should allow people to take up challenges and encourage them to take measurable risks, and give room for creativity and performing arts,' he said.
The girls felt that school could wait because some opportunities knock only once.
In an e-mail interview with The New Paper from Taipei, they said they had been interested in performing since young.
'Chances like this are hard to come by. Studying is a lifetime thing that we can always do any time.
'It's also our dad's last wish before he died that we can succeed in our pursuit so we feel we've been blessed.'
Their father died of cancer last April.
Mr Koh said their mother had wanted to pull the girls out of the Extraordinary Singer's Course because the course fee of $2,000 would tax the family's finances, especially with their father's cancer treatment costs.
The school offered a scholarship to the girls.
Their family lives in a four-room flat near Toa Payoh, said Mr Koh.
The regional music director saw a spark in them - they could sing and dance despite looking a bit 'tu' (Mandarin for country bumpkin-like).
But after the course, 'they really stood out' with their bubbly charm, dance moves and their 'unique bond'.
Mr Koh said: 'The next question was, do we want to wait for them to grow up or do it (sign them up) now?'
He weighed the pros and cons - the girls' O levels were 1 1/2 years away and there was no guarantee they would succeed as pop idols.
'At that time, nobody could tell what was right or wrong. It was a matter of choice. Either way, you've got to pay a price.'
He eventually decided that the girls were 'mentally ready'. Their mum also gave the move her blessings.
Last July, the girls dropped out of Yio Chu Kang Secondary School and a month later, they were in Taipei for vocal, dance and musictraining.
They also spent two months in Beijing and two weeks in Tokyo training under the same coaches of J-pop A-listers like Namie Amuro and Misia. Mama Bai visits them in Taipei every twomonths.
The girls said they might attend school in Taipei later, adding: 'We think education does not depend only on books but also what we see and experience.
'We lived in many cities for training and learnt their different cultures. This is something that most of our friends could not experience but, of course, education is important too.'
In Tokyo, they learnt table manners and how to show respect for elders.
With a laugh, Mr Koh recalled how he berated them for being bochap (Hokkien for don't care) Singaporean teenagers who do not serve food or tea to elders and ignore people who are talking to them.
The girls were scolded again for borrowing money after a shopping spree in Japan and for resting on their laurels after being praised.
'I told them if they don't buck up, they had better go back to Singapore, don't waste our time. They almost cried,' he said.
The girls have strict rules to abide by. They are not allowed to leave their flat at night and two undergraduate housemates keep an eye on them.
Mr Koh's staff also call to check on them.
So far, the girls have been 'quite disciplined'.
So how do they feel about their first taste of fame in cyberspace?
'We feel (it's) awesome... Most importantly, we are happy that what we have done for the blog came out successfully.'
This article was first published in The New Paper on Mar 11, 2008.