Xiaochi061's manga / #Co-workers(3)

Ch.4–5 (Side Story): Basically two guys bonding after finding out they've been played by the same person. Vol.1, Chap.1-3 & Vol.2 Chap.1 onwards: President father sends his inexperienced son to work in his stead after having collapsed and thus staying in the hospital. Said son slowly learns more about the job, working to get better, with the help of a more experienced worker there. Their relationship also progresses.