Joker Trap
Chief Mikimoto has been in a 'relationship' with co-worker Kosaka for the past month. Kosaka has now fallen in love. One night Kosaka is looking for Mikimoto... but finds him having sex with the company president! So what does Kosaka do? Through logical thinking to the wind and join them to form a threesome! (Duh!)
(Source: MangaUpdates)