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(likely a pseudonym for an independent developer or small circle, not to be confused with the Japanese studio Paon-DP). Overview of Version 1.00 Developer: Adult Visual Novel / Eroge.
Unlike mainstream horror VNs that rely on sudden gore, Passion uses slow-burn dread. The horror comes from the journal entries you find, the contradictory testimonies of the nuns, and the gradual realization that your character might be an unreliable narrator.