In this case, the three-episode rule was just right.
invite Haruki and Touma over and cook them a meal. The scenes at her house were agreeably unorthodox - sort of an open invitation for conventional anime hijinks that never happened. Instead we got a surprising intervention from her family, starting with younger brother Takahiro (you know who) and mother as they eavesdropped. Presumably their doing so was as a result of Setsuna not having any guests for three years, which she never did get around to explaining. Then Dad showed up and declared that Setsuna couldn't sing at the culture festival after all, which seems like a broad overreaction - another indication that there are important parts of Setsuna's backstory that we simply don't yet know about.