Even when she is not speaking on it, her fingers move as she sits on the subway, listens to a university lecture, or nurses a milkshake in a café.

But this is not the usual traffic of gossipy e-mails and flirtatious text messages — this is literature. For Ms Kato is writing tanka — the 31-syllable poems, like extended haiku, that have been a staple of Japanese literature for 1,300 years. And all over the country, young people like her are doing the same.

With three books of poetry to her name, Ms Kato is at the vanguard of what have become known as keitai tanka — “mobile phone poems” — that are written and distributed on mobiles. There is now a weekly keitai tanka programme on national radio, a keitai tanka magazine edited by Ms Kato, and numerous websites.

To its supporters, keitai tanka is a 21st-century literary movement, the reinvention through high technology of an ancient but moribund literary form. To traditional poets and scholars tanka are a travesty of a beautiful and delicate form, like a classical sonata performed on a screeching electric guitar.

“Classic literary styles have been broken down, and tanka have become the object of mass distribution,” laments the tanka poet Kazukiyo Hayashi. “With the use of colloquial language and liberally interpreted rhythms, I fear the world of modern tanka and classical Japanese literature share nothing in common.”

The rules governing tanka are simple. Each must contain 5 lines consisting of 31 syllables in the pattern 5-7-5-7-7. But traditional tanka, dating from the 7th century, are governed by strict conventions on vocabulary and subject matter.

Tanka students spend years mastering the use of stylised epithets called “pillow words” and use erudite literary allusions from classical literature. “Sometimes a poem can take me three or four months to refine,” says Setsuko Utsunomiya, 60, a poet from Oita. “I can’t help feeling that mobile tanka are a completely different thing.”

There have been tanka rebels before — notably Hiroshi Homura, 42, of whom one conservative poet wrote: “If this is tanka, I’ll commit ritual suicide.” But the emergence of talented young poets such as Chie Kato and the unstoppable rise of the mobile phone have spurred the tanka boom.

Ms Kato was aged 16 when she began to be noticed in tanka magazines. Inspired by her success, Japan’s national broadcaster, NHK, aired its first keitai tanka programme in 2002. Since then the programme has received 24,000 poems — mostly from young people. “One of the things mobile phones have done is to foster the ability among young people to communicate with one another in very few words. That is exactly the skill that you need to write tanka,” says Naoki Inose, a producer.

Four fifths of the keitai tanka received by NHK are about love — usually its pains, not its joys. Isolation and loneliness are also popular subjects.

“Compared with traditional tanka, these are not literary pieces,” Mr Inose says. “It’s like the difference between a beautifully composed photograph of a landscape, and the kind of snapshot which young people take with a mobile phone camera.”

ANCIENT v MODERN

On this day in spring
When the lambent air suffuses
Soft tranquility,
Why should the cherry blossoms flutter
With unsettled hearts to earth?

— Tomonori, 9th century

Kissing in the toilet of Lotteria (Japanese burger chain)!
Maybe this is definitely the first and last time.

— Chie Kato, 21st century

I recollect the past
While the summer rain falls through the dark
About my grass-thatched hut, But,
Nightingale, singing at last among the hills,
Do not call out a freshening of my tears.

— Fujiwara Shunzei, 12th century

Gonna be a rock star, if I flunk my college exams alright, Mum?

— Anonymous, 21st century

Times Recommends

• Darling under pressure on record public debt
• Mortgage drought deepens on 32% lending fall
• Oil prices firm after 10% drop to below $130