Under the Microscope: Samurai Spirits RPG

Shinsetsu Samurai Spirits Bushidou Retsuden, the Samurai Spirits RPG, was released for Neo Geo CD, Saturn, and PlayStation in 1997. Each version has exclusive bonus content. Per Wikipedia:

• Neo Geo CD: A third “mini-chapter” is enabled, wherein the player controls Hisame Shizumaru as he wanders around, running into cameo appearances of various SNK characters from other games.
• PlayStation: A “side story” mode is enabled, which enables the player to view non-interactive sequences about many of the series’ other characters.
• Saturn: An interview mode is enabled, which enables the player to view a lengthy, non-interactive sequence about the various characters, frequently breaking the fourth wall.

Wikipedia’s article also notes that the Saturn version’s bonus content “is also available in the PlayStation version, by way of a hacked save file.” What about the reverse? Is the PlayStation version’s bonus content present in the Saturn version?

BlueSky user The Price of Reason, who is working on a translation of this game, recently posted that the answer is yes:

Based on this lead, I’ve made a patch for the Saturn version that makes the PlayStation bonus content available — get it from SegaXtreme.

When applied, you can:

• Launch the PlayStation bonus content by selecting Omake from the main menu with the A button.
• Launch the Saturn bonus content by selecting Omake from the menu while holding L+Start while pressing A.

Technical details are below.

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Accessing Omake mode

When the main menu is visible, the Saturn version of the game executes the function at 06049350. It has logic that looks like this (pseudo-Python adapted from Ghidra’s decompilation):

cursor_max = 3
if check_clear_flags_060494e8() != 0:
    cursor_max = 4

if check_pressed_0603ef98(DOWN_BUTTON):
    cursor += 1

if cursor <= cursor_max:
    cursor = 0

That is, normally the main menu allocates three positions for the cursor. If you press D-pad down, the cursor’s value increments, and wraps around if it goes past the last position.

However, if check_clear_flags_060494e8 returns 1, a fourth position is allocated. These “clear flags” are values that track how much of the game has been completed. The fourth position is the Omake item, which allows you to access the bonus mode.

When you launch Omake mode, the function at 0604950c executes. It’s got logic that looks like this:

clear_flags = get_clear_flags_06048270()
if (clear_flags & 0x8080) == 0x8080:
    change_map_060473d8(0x18c)
    # ...
else:
    change_active_function(init_psx_omake_06053d34)

That is, if the value of the “clear flags” field is 0x8080, the game switches the active map. The map determines the location you start playing in. 0x18c is the map ID for the Saturn version’s bonus scene.

If the value of the “clear flags” field isn’t 0x8080, the game launches the PlayStation version’s bonus mode.

It seems that the Saturn version only allows the “clear flags” value to be 0x8080, so the PlayStation bonus mode can’t be accessed.

My patch changes the Omake mode launcher function to look like this:

held_buttons = get_held_buttons_0603eef0(0)
if (held_buttons & 0x8080) == 0x8080:
    change_map_060473d8(0x18c)
    # ...
else:
    change_active_function(init_psx_omake_06053d34)

It’s a small change: I swapped the “clear flags” check with a “held buttons” check. The comparison remains the same, but the meaning changes: 0x8080 is the logical OR of the bit patterns for the L button (0x8000) and the Start button (0x0080). So if you’re holding those, the Saturn branch executes. Otherwise, the PlayStation branch executes.

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Outro

Alas, I don’t think a PlayStation version of this patch is possible without more extensive surgery on the game’s code — its Omake mode launcher doesn’t have the check for the “clear flags.”

You can access the Saturn bonus scene with this Action Replay code, however. Apply it, then choose Haohmaru at the character select screen (he’s selected by default):

800bddd4 018c

For more on Samurai Spirits RPG hacking, see my earlier article on enabling the debug menu in the Saturn version. Many thanks to Danthrax for suggesting this article!