Regular readers of Charles Stross's Laundry Files might have noticed Bob Howard's absence from the events of The Nightmare Stacks, and his subsequent return from Tokyo at the start of The Delirium Brief.
Escape from Yokai Land explains what he was doing there.
Bob's been assigned to work with the Miyamoto Group, checking the wards that lock down Japan's warded sites—a task previously handled by his predecessor Dr. Angleton, the Eater of Souls. This mostly involves policing yokai: traditional magical beings, increasingly grown more annoying and energetic.
But then Bob's simple trip turns into a deadly confrontation with the ultimate yokai. It's massively powerful. It's pink. And it says "Hello."