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The most reliable new setup is Neko Project II Kai (NP2kai) through RetroArch’s Libretro core. Install the Kai core, put the required PC-98 firmware in RetroArch’s system/np2kai folder, load a supported PC-98 disk image, and use the NP2 menu for disk changes. The older Libretro Neko Project II core is documented as superseded by Kai. This guide covers the Libretro configuration; standalone NP2kai uses different configuration conventions and may expose different folders or menus.
What this setup uses
There are three similarly named projects that can cause confusion:
- NP2kai Libretro core: the target for this guide. It runs inside RetroArch and uses RetroArch’s system directory, input layer, disk controls and core-option menus.
- Older Libretro Neko Project II core: Libretro’s documentation describes this core as superseded by Kai. Use NP2kai for a new RetroArch installation unless you have a specific reason to preserve an older setup.
- Standalone NP2kai: a separate application or port with its own configuration files, firmware locations and menu shortcuts. A path that works in RetroArch should not be assumed to work in a standalone build.
PC-98 software is not interchangeable with ordinary IBM PC/AT floppy images. The emulator needs a PC-98-formatted image and firmware that matches the core’s expectations. Once those are in place, most games can be started without changing advanced options.
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Prepare the following:
- A current RetroArch installation with permission to write to its system directory.
- The Neko Project II Kai core for your platform.
- Firmware files obtained from hardware or software you are legally entitled to use.
- A PC-98 game image in one of NP2kai’s supported formats.
- A keyboard for initial setup. A mouse or USB game controller is optional; controller compatibility depends on your RetroArch frontend and device.
Keep the game files separate from firmware. The BIOS and font files belong in the core’s system directory; a floppy, hard-disk or CD image is the media that the emulated PC-98 boots.
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Install and select the Kai core in RetroArch
- Open RetroArch’s core-management area. In standard builds this is Main Menu > Online Updater > Core Downloader, although menu names can vary by platform package.
- Find the PC-98 entry for Neko Project II Kai and install it. If several similarly named entries appear, choose Kai rather than the older Neko Project II core.
- Return to the main menu and choose Load Core, then select Neko Project II Kai.
- Use Load Content to browse to a game image. If RetroArch asks which core should open the file, select Neko Project II Kai.
If the Kai entry is absent, update the core list or install a package that includes the Libretro core for your operating system. The exact core filename and menu wording can differ between RetroArch distributions; the important distinction is that the loaded core is Kai, not the superseded original core.
Put the PC-98 firmware in system/np2kai
RetroArch’s Kai documentation lists a dedicated subdirectory named np2kai inside the frontend’s system directory. In RetroArch, the system-directory location is shown under Settings > Directory > System/BIOS. Create an np2kai folder there, preserving the spelling and capitalization.
| File | Status for Libretro Kai | Purpose or note |
|---|---|---|
font.bmp |
Required | Font used to render PC-98 text. The documentation also identifies FONT.ROM as an alternative. |
bios.rom |
Required | Primary PC-98 BIOS image. |
itf.rom |
Required | Interface firmware image. |
sound.rom |
Required | Sound-board firmware image. |
bios9821.rom |
Optional | Additional BIOS used for PC-9821 compatibility where a title requires it. |
d8000.rom |
Optional | Optional ROM listed by the core documentation. |
| YM2608 rhythm-sample WAV files | Optional | Can add rhythm sounds when the selected emulated sound hardware uses them. |
Do not put the game image in this folder unless you deliberately want to keep it there; the core’s firmware lookup and RetroArch’s content browser are separate concerns. If the core cannot find a required file, check the exact filename, extension and directory before changing emulator settings.
Obtain firmware legally
The NP2kai project documentation says its BIOS files are obtained from an actual PC-98 with the project’s GETBIOS tool. Use firmware that you dumped from hardware you own or otherwise have permission to use. Do not download BIOS packages from an unauthorized source. The same principle applies to game disks: create or use images for software you are legally entitled to access.
The project documentation recommends the original PC-98 font.rom as the best font source. Libretro Kai also accepts the documented font filenames, so use the option that matches the files you legally obtained and the build you are running.
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Use a compatible PC-98 game image
NP2kai documents support for these media-image extensions:
| Extension | Typical role |
|---|---|
.d88 |
PC-98 floppy-disk image, often used for disk sets. |
.fdi |
Floppy-disk image. |
.hdm |
Floppy-disk image. |
.hdi |
Hard-disk image. |
.cmd |
Mounting or launch description that can refer to floppy, hard-disk or CD images. |
.nhd |
Hard-disk image. |
.hdd |
Hard-disk image. |
.zip |
Archive format recognized by supported builds; the files inside still need to be valid PC-98 media images. |
PC-98 floppy disks use PC-98 layouts such as 720 KB 2DD and 1.23 MB 2HD. An image made for an IBM PC/AT floppy drive is not automatically equivalent. If an image was created for a different computer standard, NP2kai may fail to read its directory even though the file extension looks familiar.
Boot your first game
- Confirm that the Kai core is loaded and that the firmware files are in
system/np2kai. - Choose Load Content and select one supported game image. Start with a single-disk image so that media problems are easier to isolate.
- Allow the core to boot. A game may show Japanese text, a DOS prompt, a title screen or a ROM BASIC screen before its own program starts.
- If the game starts at a DOS prompt, follow the title’s documented launch command. The emulator does not automatically turn every hard-disk image into a self-starting game.
A ROM BASIC screen asking “How many files (0-15)?” is a useful diagnostic. According to the NP2kai project documentation, this generally means the firmware was found but the selected floppy or hard-disk image did not mount correctly. Recheck that you selected the intended image, confirm it is a PC-98 image rather than an IBM PC/AT image, and restart the content after correcting it.
Change disks and manage multi-disk games
Many PC-98 titles are distributed across several floppy images. The NP2 menu provides the most direct way to swap media while a game is running.
- Open the NP2 menu with F12. The project documentation also lists the middle mouse button and L2 for its Libretro port, so one of those alternatives may be needed on a controller-oriented setup.
- Choose the floppy-drive or hard-disk image entry and select the next disk file.
- Return to the emulation screen and follow the game’s own “insert disk” or “continue” prompt.
- Reset the emulated machine after swapping a hard-disk image. NP2kai’s documentation specifically notes that hard-disk replacement needs a reset.
RetroArch may also expose Quick Menu > Disk Control. That route is useful when the loaded content is a disk set recognized by the frontend, but it does not eliminate core-specific behavior. Always verify which drive is being changed and whether the title expects a reset.
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Using .m3u and .cmd files
NP2kai’s project documentation describes UTF-8 .m3u lists for floppy disks and .cmd files for mounting floppy, hard-disk and CD images. However, the same documentation warns that .m3u support was not present in its Libretro core implementation. Therefore:
- Use an
.m3ulist only if the particular Kai build and frontend document support for it. - Use a documented
.cmdworkflow when your port supports it and the title needs a mixed or explicitly mounted set of media. - If a list opens as plain text, fails to load, or presents no disks, fall back to individual images through the NP2 menu or RetroArch Disk Control rather than assuming the image set is corrupt.
Support can differ between a standalone port and a Libretro package, so the presence of a file extension alone does not prove that the loaded core will process it.
Configure keyboard, mouse and controller input
Start with the keyboard
The keyboard is the simplest baseline because PC-98 games commonly expect keyboard commands, function keys or keypad directions. Test movement, confirm/cancel keys, and any title-specific function keys before adding a controller. If F12 does not open the NP2 menu, a RetroArch hotkey may be intercepting it; see the hotkey section below.
Choose a joypad mode that matches the game
NP2kai exposes several joypad routes, including:
- Arrow-key mode for games that read cursor keys.
- Keypad mode for titles that use the numeric keypad for movement or menus.
- Manual keyboard mapping when a game needs unusual PC-98 keys.
- Mouse mode for pointer-driven adventures, strategy games and interfaces that do not treat a gamepad as a keyboard.
A USB game controller is optional. Map it only after identifying whether the title expects keys or mouse movement; a controller can move a cursor correctly while leaving a keyboard-driven game unable to react, or it can send keys when the game is waiting for mouse input.
Fix mouse input that does nothing
First select the appropriate NP2kai mouse-input mode and verify that RetroArch is receiving movement and button events. If the emulator responds but the game does not, check whether the game’s DOS mouse driver is loaded through CONFIG.SYS. NP2kai’s project documentation specifically calls out the driver as a requirement for games that depend on DOS mouse support.
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- The six-foot cord lets you lean back and play a comfortable distance from your PC monitor.
Prevent RetroArch hotkeys from stealing game keys
RetroArch’s hotkey system can intercept keys before the emulated PC-98 receives them. Review the frontend’s Enable Hotkeys setting and its assigned hotkey combination. You can also use RetroArch’s game-focus mode, where available, to send keyboard input to the running core instead of the frontend. Change one input setting at a time and retest the key that failed, especially F12, Escape and function keys.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Adjust compatibility options only when a game needs them
NP2kai provides core options for the emulated PC-98 model, CPU base clock, CPU multiplier, RAM size, graphics controller and sound board. Leave these at their defaults for the first boot. Change them only when a title’s documentation or its behavior indicates a specific requirement.
| Option area | Why it matters | Safe approach |
|---|---|---|
| PC model | Different PC-98 generations expose different hardware capabilities and firmware behavior. | Select the model required by the game; otherwise begin with the default. |
| CPU base clock and multiplier | Changes emulated processor speed and can affect timing-sensitive software. | Do not raise speed merely to compensate for a bad image or missing driver. |
| RAM | Some software expects a particular memory size. | Use the amount stated by the game’s documentation when available. |
| Graphics controller | Older and later titles can target different display hardware. | Change it only when the title requires a different controller or graphics fail. |
| Sound board | Determines the emulated audio hardware and available sound features. | Use the title’s documented board; otherwise test the default first. |
Libretro and NP2kai documentation give a broad starting rule: the 26K sound option suits older games, while 86 is associated with newer games. That is a general guideline, not proof that every title in an era uses that board. If audio is wrong, try the board specified by the game rather than changing several options together.
Some option changes require a core restart, and changing the sound generator requires a reset. Save your current option values, apply one change, restart or reset as requested, and then test the title again. If behavior becomes less stable, restore the defaults before trying another variable.
Troubleshoot common failures
| Symptom | Most likely check | What to do |
|---|---|---|
| ROM BASIC asks “How many files (0-15)?” | The firmware is present, but the selected media did not mount. | Verify the image path and format, ensure it is a PC-98 disk image, select it again and restart the content. |
| Japanese text is missing or unreadable | Font filename, path or core mismatch. | Confirm that font.bmp or the supported FONT.ROM is in system/np2kai. Check that you are running Kai and not a standalone port with different font conventions. |
| The game boots but the mouse does nothing | Wrong joypad/mouse mode or absent DOS mouse driver. | Select mouse input, then check that the game or DOS loads its mouse driver from CONFIG.SYS. |
| A gamepad moves a cursor, but the game expects key presses | The joypad is mapped as a mouse. | Switch to arrow-key, keypad or manual keyboard mapping. Use mouse mode only for pointer-based software. |
| Keyboard keys work in menus but not in the game | RetroArch hotkeys are intercepting input. | Review Enable Hotkeys and use game-focus mode if available, then test the affected key again. |
| Sound or game behavior is incorrect | Model, clock, memory, graphics or sound-board mismatch. | Return to defaults, consult the title’s requirements, change one option, and perform the required reset or core restart. |
| A multi-disk image does not advance | Unsupported list-file method or wrong drive operation. | Use the NP2 menu or RetroArch Disk Control. Confirm whether the build supports the chosen .m3u or .cmd workflow, and reset after a hard-disk swap. |
RetroArch Kai versus standalone NP2kai
| Area | RetroArch Libretro Kai | Standalone NP2kai or another port |
|---|---|---|
| Core selection | Load Neko Project II Kai as a RetroArch core. | Launch the platform’s NP2kai executable or package. |
| Firmware location | Use RetroArch’s system directory, specifically system/np2kai for the documented files. |
Follow that port’s own firmware and configuration instructions. |
| Menu access | F12 is documented; the Libretro port also documents middle mouse and L2 alternatives. | Shortcuts and menu bindings can differ. |
| Disk control | Use the NP2 menu and, where supported, RetroArch Disk Control. | Use the standalone port’s drive controls and list-file implementation. |
| Input handling | RetroArch hotkeys, game focus and joypad mappings can affect what reaches the core. | The port may have its own input layer and conflicts. |
| Option restart behavior | Core options may require a core restart or reset. | Standalone settings may be saved or applied differently. |
This distinction explains why copying a firmware folder from a standalone guide into RetroArch, or expecting a standalone .m3u workflow to work in the Libretro core, can fail even when the files themselves are valid.
A reliable order for diagnosing a new game
- Verify that RetroArch loaded Neko Project II Kai, not the superseded core or a different platform core.
- Verify the required firmware filenames and the exact
system/np2kailocation. - Boot one supported PC-98 image by itself.
- Resolve media-format errors before changing CPU, model or sound settings.
- Test keyboard input, then configure mouse or joypad input according to the game’s control method.
- For multiple disks, use the NP2 menu first; test list files only after confirming that the particular build supports them.
- Change one compatibility option at a time and honor any reset or restart requirement.
This order separates firmware, media, input and hardware-emulation problems. It also prevents a controller mapping or clock change from masking a disk image that was never mountable.
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