Not a branching VN

Structurally this is not a branching VN. It is four sequential episodes, each of which re-runs the same locked-room premise with new pieces. Treating the absence of branches as a deficiency misreads the form — the whole point is that the setup recurs and you, the reader, are the variable.

The episode break between 4 and 5 (question arcs to answer arcs) is a real gate. The question arcs are designed to be read without having the solution. Go in knowing that, and you read the correct book.