The name comes from the moisture bomb idea, and the serum earns it. Kose Cosmeport built this Clear Turn sheet mask around a complex it calls Moisture Aqua Bomb cpx, led by sacran, a polysaccharide harvested from a rare Japanese freshwater algae that only grows in clean spring water. Kose says sacran holds up to 6,000 times its own weight in water and has five times the water-holding capacity of hyaluronic acid. Alongside it sit white fungus polysaccharide and a small-molecule hyaluronic acid, plus a ceramide-like copolymer and glycine that help skin hold onto the moisture after the mask comes off. The sheet itself is Bemliese, a thick cotton-derived fabric made in Japan with a textured surface that grips the face and carries a lot of serum. That texture has a second use: wiping with the bumpy side after removal helps lift away flaky surface skin, which is why makeup tends to sit better the next morning.