Identity
Rice lees extract — INCI Oryza Sativa (Rice) Lees Extract — is made from lees, the fermented sediment left behind when rice is brewed into wine (sake). It carries a lot of romantic marketing ("the secret behind sake-brewers' soft hands", "geisha skin"), but chemically it is a variable fermented blend: sugars, amino acids, and organic acids produced by fermentation, in proportions that depend on the rice, the culture, and the extraction.
Because it is a blend, this entry files it as blend / combination and grades it on the direct evidence for the extract — not on the individual molecules it contains. It is also a different ingredient from non-fermented Oryza Sativa (rice) extract, from rice-bran oil, and from isolated ferulic acid (a rice-derived antioxidant that has its own entry); the ferment's ferulic-acid content does not make it a ferulic-acid product.
Mechanism (as proposed)
On skin, rice lees extract behaves as a humectant and conditioning film-former: its sugars and amino acids hold water and leave a smooth, hydrated, brighter-looking surface. That is the supportable, appearance-level benefit, graded C given the limited human evidence for the fermented extract specifically.
What the evidence does not support is the folklore: "miracle brightening", skin-whitening, or pigment treatment. Brightness here means a fresher, more even-looking surface from hydration and mild conditioning — not depigmentation, which would be a treatment claim outside cosmetic scope. Fermented-rice cosmetics are a pleasant, hydrating part of the K-beauty tradition; judged on the evidence, they are conditioners, not miracles.