This is Yuzupon produced by Mitzkan, a vinegar company.
Yuzupon is a kind of vinegar sauce which has Yuzu lemon flavour.
Fresh, Japanese lemon ( or lime ? ) flavoured vinegar soy sauce.
It can be used for various meals. Dressing, Nabe, Sahimi etc.
I love it ! There are various other producers of this. Mitzkan is one of the easy brand that you can find at stores. Prices are reasonable--- I think I paid about 200 yen for this.