Kodou no Yokan - Vital Zero

Advertisement designer, Agaki is completely unaware of his attractiveness to men. This is why he’s in bad terms with his colleague and nemesis, the ace designer Haruna, despite the fact Haruna has always come to his aid more than once. One day, Agaki stumbled across Haruna’s secret! Thinking he finally had the upper hand over his archenemy, Agaki let his guard down. Next thing he knew, he got drunk and ended up getting photographed in a compromising position. Now, Agaki has no choice but to obey Haruna’s sexual advances...

(Source: Fantasy Shrine)