As more Japanese use mobile phones to shop online, Asia's biggest parcel shipper is ready.

Yamato Holdings Co. is seeing so much demand for everything from computer disks to electrical parts by customers of Inc. and other online retailers in Japan that it bet ¥140 billion ($1.4 billion) on its largest processing warehouse next to Tokyo's Haneda airport.

The company, the region's largest express shipper by sales, built the multifloor building and complex, called Haneda Chronogate, with about 200,000 sq. meters (2.2 million sq. feet) of sorting space, more than double the size of its next-biggest site, to enable same day delivery of Internet purchases in most parts of the country.