https://www.iza.ne.jp/article/20210324-5D4NYLCUN5OIPJ3T3HA6NEK5CE/ According to this, Kagawa Prefecture's "time limit" rule on playing games and using smartphones might be associated with lower such usage, however, it is associated with higher levels of addiction.
It is also criticized for being a violation of the Constitution, and there is an active lawsuit against it.