This is it! I've been curious about Higurashi's Answer arcs ever since I was introduced to the concept. About half of this is dedicated to the year before Keiichi arrives in Hinamizawa, and the other half retells the events of the second game from the viewpoint of a character with more access and insight into the workings of the village.

Although the main character's vantage point demystifies a lot of what went on, it's still a single person's perspective, which inevitably leaves certain mysteries intact.