The gacha effects should be spectacular. However, if you lie about it, you risk being judged by the law.
In one game, an item was taken out of a box as part of the gacha performance. However, there was a large discrepancy between the item in the box during the production and the actual probability of ejection. The appearance of the box contained many rare items and it looked as if the rare items could be easily obtained.
This may fall under the category of “misrepresentation of quality” as defined by Japan’s Act Against Unjustifiable Premiums and Misleading Representations, which is an act of trying to make a product look better than it actually is. This was a firestorm. In the end, there was no result on whether the law was actually violated in this case, but there is no doubt that there is at least some risk.
Please be careful when creating your production.