Most notably, it can revive Monsters from either Duelists graveyard regardless of who activates it , making this card especially useful
Combined with the option to add it to your inkwell if you want, its a no-brainer in any emerald deck
Other than give you a shot to have Steel Squirrel's first ability trigger, no
Any counters that were on it cease to exist
But I do think that varying your approach to where you're, not just spending time playing games, but also looking at other aspects of how other people play the game helps for a more holistic improvement
While it's in play, if a Creature you control with power one or less dies, you may return it to the battlefield at the beginning of the next end step if Shirei is still on the battlefield