One of my favorite short series ever, regardless of genre. I reread this series multiple times in English scanlation (from the serialization), then purchased the tankobon in Chinese.
Like others have mentioned, the provocative covers are somewhat misleading (and I personally wish they were tamer, since it's a bit embarrassing to have these out where someone else could see them). Hashimoto Aoi's art is always beautiful and there are plenty of tamer chapter-cover illustrations that would have worked well for a cover.
There are lots of sex scenes, and Hashimoto Aoi is excellent at drawing smut, but the main characters are well developed and the plot would work even without the sex scenes, which makes the sexy scenes even hotter. The pacing is done really well for a two-volume series - the progression of characters' emotions over time feels natural.
I'm not a huge fan of the "straight seme" trope in general, but it's handled fairly well here, better so than in the mangaka's other works I think (spoiler below regarding this).
Sei thinks that Misumi is beautiful when he first meets him. He notes that he didn't know he could be with a man until he hooked up with Misumi, but also says at one point that he didn't have sex or masturbate that much even when he was his wife, because he focused all of his attention on work and that seemed to be fine. Instead of a "I've only ever been with women, this man is the one exception" setup, it's more like "I was with women by default but wasn't really ever that focused on sex even though I was married, because I was so focused on work. I guess I can be interested in men, too." He's pretty much unbothered by it one way or another, and the way that his "adoptive father" Kiyo-san reacts to Sei/Misumi's relationship makes this attitude more believable (Kiyo-san completely takes it in stride when he meets Misumi and immediately finds out that Misumi and Sei hooked up), since it suggests a tolerant upbringing.
There are a few lines from this manga that I keep thinking about, because they capture the characters' personalities and thoughts so well:
1. When Misumi drunkenly tells Sei re: insisting on not having sex, "That's not our true feelings" and then insists on having sex, and
2. When Misumi calls Sei out on his jealousy and Sei says "Is it bad if I'm jealous?" with an irritated face right before telling him "I love you."