In a country where tap water is safe and the soft drink market is saturated by an incredible variety of products, Japan's mineral water consumption has stayed relatively small.

But since the debut a year ago of Asahi Soft Drinks Co.'s hit product Sanso-sui, or Oxygen Water, value-added bottled water products such as those with extra oxygen, dietary fiber or a special aroma have become the latest craze among health-conscious consumers.

"It's refreshing," Kyoko Terada, a 31-year-old bakery worker, said of the OxygenO2 mineral water she has been drinking for the past two months. The product, distributed by Saitama-based Kyodoshoji Corp., contains 15 times more oxygen than regular mineral water.