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SCRIPT_FORMAT.md

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SMT Nine Script Format (.mgs / .mgp)

Complete binary format specification for the game's dialogue script files, reverse-engineered from the 86 script files in Media/Script/ and Media/Scriptf/.

Container Format (.mgp)

MGP files are containers holding multiple named sub-scripts.

Offset 0:    7E 00          (magic)
Offset 2:    uint16 LE      entry_count
Offset 4:    entry_count × uint32 LE offsets

Each offset points to a named sub-script entry. Null entries use a self-referencing value (the offset equals the position of the offset field itself: 4 + index * 4).

Real entries at the pointed-to offset:

Offset 0:    uint8          name_length
Offset 1:    name_length bytes   ASCII name
             0x00           null terminator
             [sub-script binary data]

Standalone Format (.mgs)

MGS files contain a single sub-script with no container wrapper. The binary data starts directly at offset 0.

Sub-Script Binary Format

Offset 0:    7E 00          (magic)
Offset 2:    uint32 LE      off1    (section 1 offset, relative to magic)
Offset 6:    uint32 LE      off2    (section 2 offset — TEXT)
Offset 10:   uint32 LE      off3    (section 3 offset)
Offset 14:   uint32 LE      off4    (section 4 offset)
Offset 18:   [code bytes from 18 to off1]
             [section 1: off1 to off2]    — binary data
             [section 2: off2 to off3]    — ALL TRANSLATABLE TEXT
             [section 3: off3 to off4]    — binary data
             [section 4: off4 to end]     — binary data

All offsets are relative to the position of the 7E 00 magic marker for the sub-script (not the file start, which matters for MGP entries).

Section 2 — Text Strings

This is where all translatable dialogue lives.

Offset 0:    uint16 LE      string_count
Offset 2:    uint16 LE      extra (purpose unknown — MUST be preserved on rebuild)
Offset 4:    string_count bytes    metadata (one byte per string)
             string_count null-terminated Shift-JIS strings (sequential)

Critical detail: The header is 4 bytes (uint16 count + uint16 extra), not 2. Getting this wrong causes all MGP rebuilds to produce corrupted files.

Strings are variable-length, null-terminated, and packed sequentially. There are no fixed-size slots and no pointer table — the game reads strings sequentially using string_count and the null terminators. This means translated strings can be any length without breaking the format; section offsets are recomputed during rebuild.

Metadata Bytes

Each string has one metadata byte. The value typically equals byte_length_of_string + 1 (including the null terminator), but this is not strictly enforced for all entries. When inserting translations, the metadata byte should be updated to reflect the new string length.

Control Codes

All control codes are 2-byte FF xx sequences embedded within the string data:

Placeholder Bytes Occurrences Meaning
{surname} FF 01 324 Player surname
{name} FF 02 784 Player given name
{var} FF 04 15,998 Generic variable (item name, demon name, count)
{var7} FF 07 268 Named entity variable
{var9} FF 09 24 Race/type name variable
{br} FF 0A 268 Line break
{varb} FF 0B 135 Variable B

The extraction tool converts these to {placeholder} text in JSON output; the insertion tool converts them back to FF xx bytes.

File Inventory

Media/Script/ contains the male protagonist route (43 files, 235,741 strings). Media/Scriptf/ mirrors it for the female protagonist (43 files, 235,451 strings) with roughly 100K overlapping strings.

By Content Type

Category Files Strings % of Total
Story dialogue EVE.mgp, MAK.mgp, MSJ.mgp, RL.mgp ~45,400 19.2%
Navigator commentary NAVI_COM sub-scripts in M-prefix files ~74,000 31.4%
Location NPC dialogue M-prefix files (non-NAVI sub-scripts) ~12,000 5.1%
Demon negotiation 18 aku_*.mgs files ~103,600 43.9%
Transport ride_on/off/exit.mgs ~290 0.1%
Route variants 7 *RE.mgp files ~4 ~0%

By File

File(s) Type Sub-scripts Strings Notes
EVE.mgp Story 236 — Main story/event script
MAK.mgp Story 136 — Story script
MSJ.mgp Story 337 — Story script
RL.mgp Story 51 — "Real Life" (real world) script
MRP.mgp Location 33 14,531 Royal Palace
MIK.mgp Location 33 12,627 Ikebukuro
MSN.mgp Location 33 12,338 Shinagawa
MSB.mgp Location 40 11,895 Shibuya
MKJ.mgp Location 36 11,689 Kichijoji
MHA.mgp Location 32 11,450 Hierarchy
MUE.mgp Location 32 11,148 Ueno
MGA.mgp Location 28 666 Gaia
MMA.mgp Location 13 106 Minor area
MWM.mgp Location 1 25 World Map
aku_00–aku_15.mgs Demon 1 each ~6K–12K each Demon negotiation
aku_teki.mgs Demon 1 — Enemy demon text
aku_yuko.mgs Demon 1 — Special demon text

Translation Strategy Notes

Display width: With halfwidth rendering enabled, English characters occupy half the pixel width of Japanese kanji. Each dialogue line holds approximately 20–22 halfwidth ASCII characters. Since there are no fixed byte slots, overflow is handled by abbreviation, {br} line splitting, or rewording — never by truncating meaning.

Dual routes: Both Script/ and Scriptf/ need translation for full game coverage. The ~100K overlapping strings mean significant work can be reused.

Demon negotiation: The 103K demon negotiation strings (44% of all text) follow formulaic patterns tied to 17 demon personality types. Pattern-based or template-driven translation may be more efficient than individual string translation for this category.