Around that time ( mid-2002 ) , an easing of relations between North and South Korea gave impetus to the Japan -- Korea - tunnel project .
Also in 2002 Japanese experts had estimated that the tunnel would take 15 years and cost US $77 billion to complete .
Around that time ( mid-2002 ) , an easing of relations between North and South Korea gave impetus to the Japanese -- Korea - tunnel project .
Also in 2002 Japanese experts had estimated that the tunnel would take 15 years and cost US $77 billion to complete .