Senpai, Koko wa Ore no Deban desho?

"That does it; my life is over now, for sure...!" Though he's good at his job, due to a stubborn streak and an overly serious attitude, office worker Sakura tends to take on too much. But he has a secret - after sunset on the weekends, he becomes "someone else." However, his junior coworker Arima sees him in this other form, and Sakura even gets stuck sharing his secret with the guy...!! Can straight-laced, earnest, bespectacled Sakura handle the onslaught from his blank-faced, pushy junior on top of all the rest of his stress?! (Source: MangaPlaza)