Incorrect rules interaction with Kaito Shizuki
My opponent played Kaito, Dancing Shadows on one turn, a few turns later he played Kaito Shizuka. After spell resolution, both remained on the battlefield. This goes against the Legendaries rule that states two legendary permanents of the same name cannot be on the same players battlefield at the same time. Both of those planeswalkers are "Planeswalker - Kaito". One of them should have been sacrificed.
-
[Deleted User] commented
The planeswalker uniqueness rule has been abandoned years ago, and fused with the legend rule. So all planeswalkers are now legendary, and only the EXACT same name invokes the legend rule. The two Kaitos do no have the exact same card name, so the legend rule doesn't apply.