The rest of the numbuzin lineup is where the numbers get more specific. No.1 is the calm corner, with the Pantothenic B5 Active Soothing Serum built around pantothenic acid and niacinamide, and the Easy Peasy Cleansing Oil, which is fragrance-free and made with corn and macadamia seed oil. No.2 brings the Rose PDRN Collagen Plumping Serum, with rose PDRN, peptides and collagen, and the Cica Ceramide Repair Cream with ceramide and centella asiatica.

No.4 is the Ceramide AHA PHA Glazed Skin Prep Serum, an exfoliating serum with glycolic acid, PHA and ceramide. No.6 is the Hyaluronic Acid Deep Sleep Mask Serum, made with Iceland glacier water, hyaluronic acid and niacinamide. No.9 is the brand's firming line. The NAD+ Peptide Lifting Serum is built around NAD+ and 50 peptides, and the NAD+ Salmon PDRN Toner adds salmon PDRN, peptides and niacinamide for glass-skin hydration.

The way I would use them: cleanse with the oil at night, use the toner in the morning, and keep the serum that matches your goal as the one step that does the work.

What I would skip: layering the No.4 exfoliating serum with the No.3 Exfoliating Toner Pads on the same night. Both are built around exfoliating acids, so pick one.

numbuzin is not the only Korean brand with a good shelf, so here is the rest of the aisle. LANEIGE Cream Skin Milky Toner is a milky toner in a refillable bottle with ceramides and peptides, and the brand says to pat it in and layer for extra hydration. belif Aqua Bomb Hydrating Toner is a water-based liquid with sodium hyaluronate, honeysuckle and baobab, and it works on a cotton pad or pressed in by hand. Dr. Jart+ Ceramidin Skin Barrier Serum Toner combines the serum and toner step with Ceramide NP and panthenol, and the brand suggests following it with its Ceramidin cream.

For serums, innisfree Retinol Green Tea PDRN is a vegan retinol serum with a triple retinol complex, and the brand says irritation-prone and first-time users should start two to three times a week. innisfree Rapid Vitamin C serum uses vitamins C and E, ferulic acid and a green tea enzyme. Sulwhasoo First Care Activating Serum is applied in three pumps to damp skin, and Sulwhasoo Concentrated Ginseng Rejuvenating Serum is made with ginseng and retinol capsules. LANEIGE Water Bank Blue Hyaluronic Cream is a lightweight cream with Blue HA and squalane for the last step.

What I would skip: stacking two retinol serums at once. If you try the innisfree retinol, let it be the only one that night.

Choose by the step you are missing, not by the brand. If you have no toner, start with the No.3 Super Glowing Essence Toner or the belif Aqua Bomb. If you want one serum, pick the number that names your concern, then add a cream like the LANEIGE Water Bank to finish. Keep actives like retinol for evenings and do not add more than one new product a week. A routine that stays simple is the point of the numbers in the first place. When something new arrives, give it a couple of weeks on its own before judging it, and notice how your skin feels by evening, not just right after you apply it.