Social media / TikTok hype
Multiple reviewers explicitly mention buying because of TikTok trends or viral recommendations, sometimes purchasing before even trying the product.
Ingredient reputation (NAD+, PDRN, peptides)
Buyers cite interest in NAD+, PDRN and the '50 peptides' claim as a key draw, associating it with anti-aging and skin renewal benefits.
Repurchase / brand loyalty
A very large share of reviews are 2nd, 3rd, or repeat bottle purchases, and many say they buy the full numbuzin No.9 line together.
Recommendation from friends/influencers
Several reviewers mention being recommended the product by a friend with good skin or after reading many positive reviews online.
Value for price
Reviewers frequently note it is affordable relative to perceived quality and effect, especially compared to pricier alternatives like Laneige or TirTir.