According to My Beauty Diary, the natto masks offer nourishment and is highly effective in moisture retention. The sheet has a very faint smell of natto and it didn't bother me.
The sheet is thinner then other sheet masks I've tried before. There was plenty of essence on the mask and was little messy when the essence dripped as I put the mask on. I left it on for about 30mins. After removing the mask from my face, I put it on my neck for another 10mins. I slowly massaged and patted the remaining essence on my face dry.
The mask did what it say - moisturing and firming. My face was soft and moistured after using it. I could also feel the firmness on my skin. I used the mask before going to bed and I skipped my night moisturiser. When I woke up the next morning, my skin was still moistured after 8 hours and it wasn't oily.
It's my first MBD mask and definitely wouldn't be the last.