The titular story of the series, and also the one that made up the bulk of the 2 books, focused on Roi, a black goat spirit, and Xiu, the fire god he served. The two met when Roi was attacked by humans and about to be burned alive. Xiu saved him and gave him a human form, and the two had been together ever since as master and servant.
This was definitely not a cute and fluffy romance. Aside from their first meeting involving Xiu saving Roi from being burned alive after being beaten, shot with arrows, and stabbed, Xiu burned Roi alive when he got angry with him and Xiu's confession of his feelings to Roi is accompanied by him hitting him to the point of blood coming out so that when they have sex for the first time, Roi's face is covered in bruises and blood. That's all in the first chapter. I was honestly surprised at how brutal it was. The book instantly stopped that after the first chapter and didn't have anything like that between the two of them again until the end of the second book with a two page "funny" story about how any time Roi would try to grow a beard, Xiu would burn it off his face. I could have down without that.
Outside of those two sections, I enjoyed them as a couple, even if I just kept wishing they would simply talk to one another. They both had severe self esteem issues and thought the other would leave them once they realized there was "better" our there, not thinking about the fact that they've both been pining for the other for centuries.
Their story did throw in a sexual assault scene, unfortunately. It's thankfully not between the two of them. All their scenes were consensual. Instead, a side character started stripping Roi to have sex with him despite Roi's repeated protests. It's another one of those things I could have done without.
There were also 3 other stories in series, 1 in the first book and 2 in the second. The first was another supernatural story, although the supernatural elements were only hinted at in the beginning. The main character, Takara, was just fired again and his neighbor, Katabami, was hoping he'd finally let him take care of him. But Takara was determined to get a job and an old acquaintance had an opening to interview for. But nobody was quite who they seem in this story. This was an interesting one, but definitely a twisted romance once the reveal of what was going on came.(show spoiler)
The next story featured side characters from the main story. It was a short story about the couple sorting out an issue with their relationship after having just gotten back together by communicating (it took a little bit of time to get to the communication). It was pretty sweet.
The last story was my least favorite and also felt out of place as the only contemporary story in a book of supernatural stories. It opened with a nephew and uncle having sex on page one of the story and things didn't get better. Additional revelations that the uncle had been the primary caretaker of the kid since he had been an infant because the parents kept leaving him with the uncle to go on extended vacations, that the nephew was still a kid, that the nephew didn't eat so that he'd stay skinny like he thought the uncle would like, and that the nephew didn't want to grow up because he though the uncle only liked young boys just made everything unpleasant. I was very happy it was a one-shot and the book went right back to Roi and Xiu after this.
Overall, it was an enjoyable series (except for the incest story, Someday's Dream, which I would just skip). It's certainly not for everyone, but if fantasy BL that gets a bit dark without going grimdark is your thing, this might be one to check out.