Pichu/Ditto

[mirosama]

Player A has an active Pichu HS and uses Playground. Both players fill their benches with basics and both of them choose a Ditto TR as one of the basics. Now that both players have 5 benched pokemon and Ditto with Dittobolic, who discards a basic from their bench first? When do the players discard a benched pokemon? And if either of them discards their Ditto...?

Thanks

Pichu
Attack:
Playground: Each player may search his or her deck for as many Basic Pokémon as he or she likes, and put them onto his or her Bench, and shuffle his or her deck afterward. (You put your Pokémon onto the Bench first). Pichu is now Asleep.

Ditto
body: Dittobolic
The number of Benched Pokémon your opponent can have is now 4. If your opponent has 5 Benched Pokémon, your opponent must discard 1 of them and all cards attached to it.

 

[PokePop]

"You put your Pokemon on the Bench first".
So Pichu's player has put his Ditto onto the bench first.
Therefore, his opponent is only going to be able to put out a maximum of 4 benched Pokemon and won't discard any, since he never had a 5th one out.

Once he puts out his Ditto, then player A has to choose and discard one.