So possible book 16 spoilers have begun coming out on Japanese blogs/fora. As usual, please note that these are NOT RELIABLE. This post will continue to be updated as I find more spoilers.

There are four illustrations: Shuurei+Jin+Shuuei, Shuurei+Jin, Shuuei+Shusui, and Ryuuki+Ou Ki. (using pluses because if I used commas, things would get confusing). [my thoughts: huh, so looks like Jin plays a large role?]

Ryuu Shibi, a character who shows up in Unmei no Deai no Yoru (and is also mentioned in book 15) shows up.

In Heki Province, the governor goes missing or something, due to the destruction brought by the locusts, so Ouyou Gyoku (Undersecretary of Public Works) becomes acting governor; he calls for the central army to be sent there.

Riou’s grandfather is indeed Ou Ki. [Hmmm! As I suspected. Well, as most of the readers suspected, ha.]

In the palace of the Hyou clan, Shuurei, Riou, and Jin research methods to get rid of the locusts, while Shuuei enters the prison that Shusui is trapped in and rescues her.

Ryuuki visits Ou Ki, who is setting out for Kou Province. Ou Ki criticizes him clearly, and Ryuuki cries.

Shuurei is now able to leave the Hyou clan’s palace, and says she will indeed leave.

Ryuu Shibi visits the main mansion of the Kou clan (in Kou province). He tells Reishin that he thinks that Reishin is the only one who can change Yuushun’s fate.

Kouyuu goes to visit Yuushun in the middle of the night…. and from there the book ends?

Yuri, Jyuusan-hime, Karin, Ensei, Seiga, and Ouyou Jun don’t really appear much, if at all.

According to the afterword, it’ll be awhile before the next book comes out.

EDIT 1:

Riou (Sr.) says that if Shuurei et al want to do something about the locusts, they need to find Shusui. While Shuuei (as mentioned above) seeks Shusui in the prison of time (which seems to be place used to test the strength of determination of priestesses), Shuurei, Riou, and Jin research the locusts and find there’s a disease that only strikes locusts, and that humans can somehow make this disease start, thus wiping out the locusts. Shusui is able to open a corridor to the Hyou temple which deals with this, but the temple priest says he can’t act without Ruka’s permission. Shusui agrees to become Ruka’s successor as high priestess and work with her for Ruka’s remaining lifetime. Ruka opens the gates of the Hyou clan’s palace.

Jin’s master is indeed Ou Ki. (He is the one who reveals that Hien-hime, Riou (Jr.)’s mother, is Ou Ki’s only daughter) However, there is apparently another high official messing with the Hyou clan. Shuurei learns of this person’s name from Ruka, but the reader doesn’t.

Kurou’s wife appears.

Ryuu Shibi also think there’s someone out there who is as smart as Yuushun　who might be behind some of this stuff?

EDIT 3: Son Ryouou and Shouka have some conversation about why Shouka supports Ryuuki as king.
Jin hasn’t met Hien-hime. From Ou Ki’s words, readers think it’s difficult to tell whether Hien-hime is currently dead or alive.

Undersecretary Kei Yuuri (Houju/Kijin’s undersecretary) apparently argues with Anju (who is rather scary in general).

Eh… Most of the spoilers are pretty vague; they tend to end up praising some character another for being cool or competent. Riou and Shusui’s character development is prominent. The storyline is basically split into two parts, I get the impression, just like in the last book. One of the storylines focuses on the Hyou clan, and the other focuses on the stuff going on in the capital. Some bloggers remark that within the capital plotline, most of the dramatic focus is on the high officials, and that barring the scene where he talks to Ou Ki, Ryuuki appears far less frequently than one might have thought he would.

Also:

Shouka didn’t really destroy the real sacred mirror. He destroyed another mirror that Ruka was using to transmit her soul, but another party destroyed the sacred mirror Karin is trying to replace.

Jin didn’t come to try and kill Ruka; he instead came to find information about the locust plague.

Son Ryouou is a famed warrior, on par with Sou Taifu and Shiba Jin’s grandfather.

Sakujun tries to kill Shusui, but Shuuei fights with him and makes him go away. Apparently now Shuuei is stronger than Seiran.

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