There are many aspects of this product. First of all, POM is a citrus brand for local produce from a local beverage maker in Ehime Prefecture - a brand strong enough to make it all across Japan. Mikan mandarin tangerines are grown in this area which is located on the Seto Inland Sea. Therefore, naturally, this product uses local mikan, but also contains a local sea salt which is also well known, Hakata Salt from an island of the same name. So the salt is well known and of regional interest, which fits well with a beverage maker from the same region, but also fits in well with the popularity of salty products during the hot summer months. 伯方の塩 愛媛飲料 ミカン
http://www.ehime-inryo.co.jp/topics/shio_natsumikan2.php
Photo is a web capture for explanatory purposes, copyright belongs to the company.