Though Ariane 5 launch with BepiColombo mission explorers aboard was originally scheduled for 10:45 p.m., October 18, (local time in French Guinea) 2018, due to schedule adjustments the launch has moved later as follows:

Launch Date:

10:45:28 p.m., October 19, 2018 (local time in French Guinea)
(10:45:28 a.m., October 20, 2018 in Japan Time,)

Reserved Launch Period:

through November 29, 2018 (in local time in French Guinea)

Location:

Guiana Space Centre, Europe's spaceport in Kourou

[Reference]
Mission Overview: The International Mercury Exploration "BepiColombo" Mission and MIO

BepiColombo, an ESA-JAXA joint mission to explore Mercury, sends two spacecraft to orbit around Mercury for observations. Each is tasked with distinctive observation objects. MIO aims at elucidating the magnetic field and magnetosphere of Mercury. The MPO mission is observing the planet's surface and internal composition. JAXA is in charge of the development of the MIO spacecraft and controlling its operation at the target orbit because MIO's mission objectives lie in Japan's area of expertise. ESA controls BepiColombo launch and flight to Mercury and orbital insertions. The development and operation of the MPO is also part of the mission performed by ESA.
MIO and MPO are payload launched by the Ariane 5 spacecraft. After entering the planet's orbit, detached satellites are scheduled for approximately year-long observation mission, which both agencies will cooperatively engage in.

「Computer-generated image of MIO and Mercury

Computer-generated image of MIO and Mercury (c) JAXA

Image of MIO as made public to the press in 2015

Image of MIO as made public to the press in 2015 (c) JAXA