Black Diamond by FUWA Shinri

Summary

Plot: Yuu is a young and handsome executive, a ruthless businessman and a charming party guest ― but at home he’s just a wilful brat. Suffering under the pall of an abusive childhood and a dark family secret, Yuu’s only friend and confidant is his loyal secretary, Asa. Asa is hopelessly smitten with his boss, but no matter the intensity of his devotion, he suppresses it out of obedience. But when Asa’s manipulative university senpai suddenly emerges in the business world, both men must to face up to their pasts and the truth of their relationship.