KDDI, has had success among older people with its Tu-ka phone, selling more than 100, 000 subscriptions.

ECONOMIST: The grey market

The music is drawn from an extensive traditional repertoire named after ethnicities, towns or flowers ( Tu People s ''ling , '' White Peony ''ling'' ), and lyrics are improvised in keeping with certain rules for example, verses have three, four, five or six lines, each made up of seven syllables.

UNESCO: Culture

Tu should only be used with people you know well, such as office colleagues.

ECONOMIST: Business travel

The plane, a Tupolev Tu-204, is capable of carrying 210 people.

CNN: Death toll rises in Russia plane crash

"We've seen the growing popularity of communication apps on smartphones but we believe we've gone one better with Tu Me using our knowledge and insights of how people use their devices, " said Telefonica Digital's chief commercial officer Stephen Shurrock.

BBC: Telefonica unveils data-based communication app Tu Me