Real Man

Yoo Hyun becomes the youngest CEO of Hansung, a successful electronics company built on a toxic work culture, but nobody he cares about is there to celebrate with him. After a night of drinking and wondering if he could change the past, he wakes up the next morning 20 years younger than at the beginning of his career. Armed with the experience and insights that made him CEO, Yoo Hyun begins to revisit broken relationships and battle the enablers of Hansung’s cut-throat work environment. But he does not yet know how changing the past will affect his future...
(Source: MangaUpdates)
~~ Adapted from the web novel "Sangnamja" (상남자) by Kim Tae Goong (김태궁).