Yes as Gregger said that plug is for the Yamaha led tail lights reverse lights. The plug and play kit also comes with a relay that plugs into an empty plug under the passenger side front wheel arch, that plug has an orange stripe on it.
You can use that rear empty plug to activate a back up light when selecting reverse, but the lamp must be insulated from the chassis when bolted up as the system uses a negative switched circuit. If you ground the light you will blow the reverse switch on the gearbox as has happened many times 🤣