KingC

Surprisingly, Futtara Doshaburi is a rather calm drama to watch and relies solely on the characters to carry the story. It deals with mature topics regarding intimacy and communication.
Hagiwara seemingly leads a perfect life with his longtime girlfriend Kaori - with the intimate aspect missing.
Sei's situation was different -- he was forever stuck in a twisted friendzone with Fujisawa, who claims to take care of him forever, yet doesn't allow Sei to lay a finger on him.
An accidental email had these two developing a rapport, which strengthens after they discover that they are coworkers.

I don't condone cheating, and there were alternate choices that these characters could've made, but they've (or rather Hagiwara) had been suppressed and confused for too long that he simply lost his composure and did what he did in the spur of the moment.

I could understand why certain mishaps happened, but it would've ended the exact way, even sans the cheating. But, this is a drama and we have a story to tell.

The OST was really good -- both the opening and the closing themes, along with the BGM, were apt for the theme. (The opening song is Bitter Nectar by One Love One Heart, which is the title of my review.)
In terms of acting and characters, everyone were able to convincingly portray their roles well -- but one highlight would be Muto Jun close to the end of EP5.
I was able to sympathize with them.

All in all, such a drama is a first for me, but I don't regret the time I spent on this.