〜としたら
flags the premise as purely hypothetical
「としたら」 sets up a purely hypothetical premise, then discusses things on the basis of it.
⚠ How it differs from 「〜たら」:
• 〜たら = it could actually happen
• 〜としたら = explicitly flags "this is only a supposition"
• 〜なら = picks up the topic the other person just raised
So the moment Miho says this, the absurd premise is formally established, and the three of them start discussing it with a straight face.
(Episode 7, scene 5, 「住むとしたら どのフロアにする?」, is the same usage: they know it can't happen, yet seriously pick one.)













