As usual, there are a lot of Asian brand masks that boasts their whitening qualities (i.e. provides brightening effect, reduces sunspots or pigmentation etc etc).
Regene white reborn mask is not particularly expensive, I think you can find these online for maybe < $5USD per sheet or so. The back of box says RRP 2100 yen (for the box of 4 sheets).
The main ingredients are Vitamin B5, rice bran extract, Penederm R something.
Back of box, also has Japanese texts.
Here's the English instructions and explanation on how to use, you can click on my photo to enlarge which will be readable.
Overall 2/5. I noticed no immediate hydration afterwards despite 20 minutes application, it fits my face loosely, not very well cut around the nose area. I do not wake up with brightened complexion the next day either (I don't believe in whitening products all that much, but I do expect brightening effects especially from sheet masks that are generally quite hydrating).
Will not repurchase.