6000: The Deep Sea of Madness 6000 ロクセン
Author: Nokuto Koike
Launched in 2010, 4 volumes and completed

Somewhere in the Philipines Sea, 6000 metres under water where neither the eyes of God or man can see lies a scientific facility once owned by a Japanese company. A tragic “accident” occurred in this underwater lab and it was abandoned for three years until a Chinese company buys the Japanese business and re-activates the facility.
The only way to access this facility is by an elevator of sorts that is
connected to a floating platform with the master controls on the surface. This is how everybody gets down.
Taking the ride is Kengo Kadokura, our lead character. He is a liason between his Chinese bosses and the Japanese workers but even before he takes the plunge under water he has misgivings about the endeavour not least because the two sides he is working with distrust each other.