Brand trust and line reputation
Many reviewers say they buy 'blindly' because they already trust numbuzin or the No.5 Glutathione C line from prior products, describing the brand as 'always reliable' or 'pure magic'.
Repeat purchase / loyalty
A large share of reviews explicitly mention this being their 2nd, 3rd or 4th bottle, often citing satisfaction with previous purchases as the reason to buy again.
Large size = better value
The 300ml 'large volume' format is frequently cited as a key purchase driver, with buyers noting it lasts long and offers better cost-per-use than smaller bottles sold in their home country.
Influencer/word-of-mouth recommendation
Several reviewers mention buying after seeing recommendations from YouTubers, TikTok, or friends/family (e.g., 'Ivelisse the Fashionista', 'madaboutskin').
Sample-to-full-size conversion
Multiple buyers say they received a free sample with another order and liked it enough to purchase the full-size bottle.