Loyalty to the No.5 line
Many buyers already use the No.5 serum, toner, or pads and purchased the cream to complete the routine, expecting a synergistic brightening effect.
Reputation for dark spot/hyperpigmentation efficacy
Reviewers cite word-of-mouth and prior positive experience with glutathione-based numbuzin products as their main reason for trying this cream on sun spots, freckles, and acne marks.
Repurchase/restocking
A large number of reviews explicitly mention this being a 2nd, 3rd, or 4th jar purchase, indicating strong repeat buying behavior.
Influencer/online hype
Several reviewers say they bought it after seeing it trending on YouTube, social media, or in other customer reviews before trying it themselves.
Gifting
Multiple reviews describe buying or receiving the cream as a gift for family members (mother, father) who then also enjoyed it.