So, which is which with それで

Grammar Explanation: The reason or result with それで

Mina tells Sanae that if you clasp your hands together, you can know whether you were a boy or a girl in a past life. When Mina interlocks her fingers, her left thumb is on top. For Sanae, it’s her right thumb. In the past, one was a boy, and the other was a girl.

サナエ:: 「それで、どっちがどっちなの？」; “So, which is which?”; Literal: “So, which one is which?”

Key Points

1どっちがどっち = “which one is which”

This asks how two options map onto two outcomes.
In context, Sanae wants to know which hand position means “boy” and which means “girl”.

2が marks the item to be identified

“どっちが” sets up the unknown item whose identity or role is being sorted out.
The sentence is essentially asking: “So, which one corresponds to which result?”

それで at the start of a sentence refers back to something previously said and introduces the result, much like “so” or “therefore” or “and then”.