re: index + a new open backlog item for the undecoded Japanese banks

docs/re/BACKLOG.md

@@ -6,6 +6,29 @@ unknown, what evidence exists, and what the first step would be. Move an item in
 
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+## ⚠️ OPEN (2026-08-26) — the Japanese voice banks are not decoded
+
+The `sound.pak` census (see
+[`structures/sound-pak-contents.md`](structures/sound-pak-contents.md)) shows
+the archive is 5 100 `jpn\` banks + 4 382 `eng\` banks + 35 music banks, and
+that **the leading-region rule holds for 0 of the 5 100 Japanese banks** — 4 301
+have a first `RIFF` at an offset that is not `1392 + n·2048`, and 799 have no
+`RIFF` at all. The rule was derived on English banks and reproduces those
+exactly, so this is a limit of the finding, not a defect in the reader.
+
+Since `FILES` names the **Japanese** set and the game substitutes the language
+directory, the undecoded half is the one the table actually points at.
+
+**First step**: take one misaligned `jpn\` bank and one `RIFF`-less one, and
+locate the audio by scanning for XMA1 packet structure rather than assuming a
+fixed data offset. The English aligned banks are the control — the same scan
+must find their known leading region.
+
+**Also open**: 2 of the 9 519 TOC entries are unaccounted for, and 55 English
+banks have their first `RIFF` at or before offset 1392.
+
+---
+
 ## ✅ SOLVED (2026-08-26) — the mission scripts are readable as dialogue
 
 Built-in **64** (`request_script_message`) stages a symbol-table-1 reference in