The short answer
Japan's Keihyo-ho prohibits representations that mislead consumers into thinking quality or price is better or more advantageous than it is. Japanese ads, landing pages, and content should be reviewed against this standard up front.
A 'superiority' misrepresentation makes quality or performance appear significantly better than reality. Unsubstantiated claims like 'best,' 'No.1,' or 'guaranteed results' carry high risk.
An 'advantage' misrepresentation misleads on price or terms. Take care with reference prices for discounts, limited conditions, and disclosure of additional costs.
This is general guidance; the legality of specific expressions requires professional confirmation. RIVACTA reviews expression before spend, but final responsibility rests with the advertiser.