Handy Japan Co., a startup providing free-to-use smartphones docked in hotel rooms, announced on Monday a capital tie-up with SoftBank Corp. to boost its service for tourists with "internet of things" technologies.

It was just about a year ago when the free handset service, which originated in Hong Kong in 2012 and has now spread to 82 countries, came to Japan. The firm said its service is expected to reach around 1,700 hotels, or nearly 30 percent of all hotels in Japan, within this year.

It was this fast growth that apparently caught the attention of mobile tech behemoth SoftBank.