Does your Micra vehicle have seat heaters? If not, connector is most likely for it. Mine doesn't have seat heaters and there is same connectors under both seats.
Probably for the Pressure thingy in the seat..
When someone sits in the seat without a seatbelt and you drive above 30km/h it starts beeping.
Probably disconnected for a reason? I have it too. Probably done by the previous owner