For early JDM, the empty position is 'not in use' so you are not missing anything.
The one next to it at the right top of your photo is the Front Fog light relay, NO type.
This should give you some idea.
Note that this is for RHD early models.
Please ignore the top two relays.
Mine is 94 JDM but being in UK, I added the Rear Fog circuit.
Originally, it was empty from the factory, just like yours.
This empty position was used for the rear fog circuit on the early European models.
Also, I converted the Front Fog light circuit to install the aftermarket DRL.
Instead of using the OEM NO type, using the NC one for my purpose.
You will find several different NC type relay inside the same relay box depending on the country spec.
And before you ask, the ones at the other relay box.
Kaz