Kingyo (Casio Pro Trek Smart WSD-F30) is Casio's smallest watch. Like other Casios, it has a secondary, sunlight readable display. The port is currently in progress.
Kingyo is a large rugged watch with hiking-focused features. Compared to ayu, this watch is significantly smaller. The secondary display is upgraded to allow continuously showing step counts, altitude or air pressure and features a ring of pixels around the edge which are used for showing the compass heading. The colour display is also significantly higher resolution, fully round instead of a flat tyre and OLED instead of LCD.
This port is not yet ready. Some critical bugs with the display and power management cause this watch to enter various glitched states.
Another issue is that this watch needs a 64 bit kernel and a 32 bit userspace. The watch can't be run entirely in 64 bit mode because the android hardware binaries are 32 bit. This sort of multiarch system is not easily supported by openembedded/bitbake. Currently the watch has to be built as two separate machines, with the second one building only the boot image. This also requires several hacks on top of the current build system to get working, and it's not likely to be merged in this state.
The second display has 6 7-segment digits in the center, 6 7-segment digits at the bottom, a 23x5 pixel matrix at the top, two separator lines above and below the central large digits, a ring of pixels around the edge and a smattering of icons and text indicators everywhere else. Curiously enough, kingyo features a BPM segment on the LCD, suggesting the WSD-F30 was intended to have a heartrate sensor, as seen on medaka.
USB is not exposed on the outside of these watches. Accessing USB requires some disassembly of the watch, but does not compromise water resistance. The USB access procedure for this watch is not known.
The watches can be disassembled by removing 6 tri-wing screws on the back. The watch is sealed with a gasket, so water resistance is not compromised by disassembly. Replacement parts are available, but expensive.
Miscellaneous hardware docs
The central key is the power button. The top and bottom keys are volume up and down respectively.
Manually getting to fastboot
Hold the top key while powering on the watch. Navigate the menu using the top key and select using the power button.