In Japan's smartphone game market, displaying the odds for paid gacha (loot box) draws has become standard industry practice. After the 2012 "complete gacha" (kompu gacha) controversy, industry groups established self-regulatory rules, and platforms such as the App Store also began asking for odds disclosure.
In practice, however, not every paid gacha in every game discloses its odds. According to a research paper published in the Journal of Behavioral Addictions, 91 of the 100 top-grossing iPhone games in Japan contained paid gacha. Of those 91, only 38 (41.8%) fully disclosed the odds for every gacha the researchers encountered. For the remaining 53 (58.2%), complete disclosure could not be confirmed for at least some gacha. The study shows that while odds disclosure is widespread in Japan's game industry, its implementation varies considerably.
Japan's Gacha Rules and What "Complete Disclosure" Means
Regulation of paid gacha in Japan combines legal rules with industry self-regulation. The clearest example of legal regulation is complete gacha, which became a social issue in 2012. It refers to a mechanism in which players receive an additional reward by collecting a specific combination of different items obtained from paid gacha. According to the Consumer Affairs Agency's explanation, such a scheme can constitute "card matching" (kado awase), which is prohibited under the Act against Unjustifiable Premiums and Misleading Representations, if certain conditions are met. Ordinary paid gacha are not banned across the board.
As for the odds of individual draws, industry groups have mainly developed the rules. The guidelines of the Japan Online Game Association (JOGA) call for making information about items obtainable from gacha easy to check, and set several disclosure standards for rare items, including provision rates and the estimated amount of money needed to obtain them. The guidelines of the Computer Entertainment Supplier's Association (CESA) establish as a principle that all obtainable items and the provision rate of each should be displayed. The two groups' requirements differ, and neither imposes a uniform legal obligation on all game operators.
In this study, "complete disclosure" was defined as a state in which the odds were adequately disclosed for every paid gacha encountered during the investigation. A game that displays odds for its regular gacha but lacks necessary information for limited-time or step-up gacha, for example, is not judged to be in complete disclosure. This standard assesses how thoroughly information is available to players, and a game that falls short of complete disclosure has not necessarily violated any law or industry guideline.
Audit of the Top 100 Games: Complete Disclosure at 41.8%
The research team conducted a "content audit," directly checking in-game displays, of the top 100 grossing iPhone games in Japan as of August 31, 2025. Each title was played for at least one hour in the Japanese-language environment from a newly created account, and the team recorded the gacha mechanics and odds displays it encountered. The methods and evaluation criteria were pre-registered on the Open Science Framework (OSF), and multiple Japanese speakers took part in the judgments.
The findings were released as a preprint on April 17, 2026, and presented at related conferences before being published in a peer-reviewed journal. Note that an early conference presentation reported five cases suspected of being complete gacha, but the final paper revised this to four.
The main results of the study are as follows.
| Measure | Result | Population / condition |
|---|---|---|
| Games with paid gacha | 91 games (91.0%) | Top 100 grossing games |
| Odds disclosed for at least one gacha | 82 games (90.1%) | 91 games with paid gacha |
| Complete disclosure for all gacha checked | 38 games (41.8%) | Same as above |
| Games not meeting complete disclosure | 53 games (58.2%) | Same as above |
| Suspected complete gacha | 4 games | Judged under the researchers' audit criteria |
| Missing gacha-presence notice on the App Store | 16 games (17.6%) | 91 games with paid gacha |
| Missing gacha-presence notice on Google Play | 33.0% | Store listings for the same 91 games |
Of the 91 games with paid gacha, 82 (90.1%) disclosed odds for at least one gacha. On that figure alone, odds display could be called widespread in Japan. But only 38 games (41.8%) achieved complete disclosure across all gacha identified, a gap of about 48 percentage points.
Of the 53 games that did not reach complete disclosure, 44 disclosed odds for some gacha but did not cover all of them. In the remaining nine, the researchers found no odds display for the gacha they encountered. In other words, having an odds display somewhere in a game is not the same as players being able to check the odds for every gacha they might use.
The team also identified mechanisms suspected of being complete gacha in four games. However, this is a determination based on the researchers' own audit criteria, not an administrative sanction by the Consumer Affairs Agency or a finding of illegality by a court. A real legal assessment would require detailed examination of each mechanism, including the conditions for providing rewards and their relationship to transactions.
App Store Notices Also Vary; Japan's Complete Disclosure Rate Exceeds the UK's
The researchers also examined whether app store product pages clearly indicate the presence of paid gacha. This information is meant to tell users about gacha before download, and it differs from in-game displays of the odds for individual items.
Of the 91 games with paid gacha, 16 (17.6%) lacked a visible presence notice on Apple's App Store. On Google Play, by contrast, 33.0% of the same games' listings lacked one. The same game can thus differ in disclosure depending on the platform. However, the team actually played the iPhone versions and did not verify in-game displays on Android.
Compared with earlier overseas research, Japan's disclosure picture looks relatively good. A study of top App Store titles in the UK in early 2024 found a 90.4% rate of missing gacha-presence notices and a 13.3% rate of complete in-game odds disclosure. The corresponding figures in this Japanese study are 17.6% and 41.8%. Because the targets and timing of the studies differ, however, the gap cannot simply be interpreted as the effect of each country's regulation.
The paper also suggests that changes Apple made in mid-2025 to its developer questionnaire and management screen may have contributed to improved presence notices. But this study did not compare the situation before and after the change under identical conditions, and no causal relationship has been confirmed. As for Japan's self-regulation, the results hint at some effect but fall short of showing that complete disclosure is firmly established.
Study Limitations and What Comes Next
The study quantifies the state of odds disclosure for paid gacha in Japan, but its results must be interpreted with care.
First, the investigation was limited to early play after creating a new account. Many mobile games have gacha that are unlocked later, through leveling up or limited-time events. Even games judged to have complete disclosure therefore did not necessarily have every in-game gacha examined. Conversely, even where odds could not be confirmed during early play, the information may have appeared on another screen or on an official website.
Second, the targets were Japan's 100 top-grossing iPhone games, so Android-only titles and smaller-grossing games were not included. The 91.0% prevalence of paid gacha and the 41.8% complete disclosure rate therefore cannot be applied to Japan's game market as a whole.
Third, the study evaluated game mechanics and displayed content, not players' spending behavior or health effects. The data cannot show whether inadequate odds disclosure increases spending or raises risks such as gaming disorder. It is necessary to distinguish between inadequate disclosure being a consumer protection issue and proving that actual harm resulted from it.
The research team recommends measures including clearer guidelines, multilingual outreach, stronger display requirements on the platform side, and consideration of legal regulation. The effectiveness of these measures was not demonstrated by this study.
What the study shows is that, although gacha odds displays are widespread in Japan, complete disclosure could not be confirmed in a majority of the games examined. Going forward, the challenge will be to build mechanisms that let players reliably find the necessary information for each gacha, in addition to developing self-regulation. Further research is also needed on how much thorough disclosure actually contributes to consumer protection.