Uchuujin to Deau mae ni Yomu Hon

Story

"What are you made of?" A question from "outside" that cannot be answered using the "common sense" of the earth. If you answer incorrectly, what awaits you is catastrophe or extinction. Tsubura Uruki, a graduate student, is drawn into an extreme interstellar companionship after encountering a monolith. With the survival of humanity at stake, she faces the ultimate question posed by aliens.

Synopsis via AniList (English).