In the Walnut is contemporary BL manga with occasional mystery elements. It's licensed (or was licensed? not sure, seems like it might be out of print) by Digital Manga Publishing under their Juné imprint.
I usually try to list translators when I can, but for some reason this doesn't seem to have a translator credited anywhere on the volume, not even a translation company unless Juné did it in-house.
This review includes spoilers.
Review:
Tanizaki runs his grandfather's old art gallery, In the Walnut, which specializes in restoring and selling artwork in instances where the artwork's owner might not be interested in attracting too much attention or answering too many questions. Nakai is Tanizaki's lover, an aspiring filmmaker whose only subject is Tanizaki.
The volume is very episodic. In the first story, a piece of modern art by Lui Shiina is stolen from a gallery. Later, a young man named Kusama brings Tanizaki a painting and asks him to strip it down to it undercoat, no questions asked. If you think that sounds fishy, you are correct.
In the second story, "Liar Angel," Nakai hits his head and is taken to the hospital. When Tanizaki goes to pick him up, he meets a young boy named Ryota who desperately wants to buy Paul Klee's "Forgetful Angel," his sister's favorite painting. His sister has always had bad eyesight and is beginning to go blind. Ryota wants her to be able to see the original painting before her surgery.
In the third story, "I'm Not Hamlet," a mysterious client wants to sell a painting she inherited. It's supposedly by Thomas Gainsborough (spelled primarily as "Gainsboro" in the text, but also "Gainsborough"), but it isn't any of the ones listed in his body of work. The client has paperwork identifying it as the real deal, but Tanizaki still can't decide whether to take this risk - it would mean taking out a large loan, and if he can't find a buyer it would go badly for him. Then the situation is complicated by the arrival of one of Tanizaki's grandfather's old rivals.
The volume ends with several extras (almost a quarter of the total page count, which is why I'm reviewing it as part of the whole) that reveal how Tanizaki and Nakai first met and became a couple, how Tanizaki became a model and why he stopped, and how the two of them ended up where they were at the beginning of the first story.