Incomplete compliance: Loot box prevalence, presence disclosures, probability disclosures, and Compu Gacha policy in Japanese mobile games

Background and aims: Loot boxes or gacha are bought in video games to obtain randomised rewards. Their gambling-like characteristics and associations with both gambling and videogaming disorder worry parents and regulators. As the third-largest videogaming market, Japan has a decade-long history of regulating loot boxes. Several regulations co-exist. Games must disclose the probabilities of obtaining different random rewards. A particular implementation ('Compu Gacha') that provides an extra reward after players pay to collect a specific combination of two or more other rewards is prohibited. We investigated loot box prevalence amongst Japanese mobile games and whether they complied with various regulations. Methods: In late 2025, we assessed the presence of loot boxes, Compu Gacha, and in-game probability disclosures in the 100 highest-grossing iPhone games in Japan based on the first hour of gameplay from account creation. We also checked whether games disclosed loot box presence on app stores. Results: Amongst 91 games with loot boxes, 17.6 and 33.0% failed to disclose their presence on the Apple App Store and the Google Play Store, respectively. Most games with loot boxes (90.1%) provided probability disclosures for at least one loot box identified, but only 41.8% disclosed probabilities for all loot boxes found. Four games contained suspected Compu Gacha. Discussion and Conclusions: Loot box prevalence is very high amongst Japanese mobile games. Most companies, including local Japanese ones, only partially complied with long-established probability disclosure industry self-regulations. Rare cases of suspected prohibited Compu Gacha were identified. Recent Apple App Store policy and platform design changes significantly improved loot box presence disclosure transparency. Clearer and translated English compliance guidelines, stricter enforcement, and legislation can contribute towards better consumer protection.