Thankfully, it did not take too long to find A History of Yōkai. Kindle had it for 3,200 yen (about $19.99). Once it got downloaded, Yuki starting skimming through the book.

"Come to think of it, these attacks all have to have something in common," Yuki stated.

"What?" Ryo asked.

"Our boss and his wife both had their necks torn open. My sister-" Yuki hesitated before resuming, "-had her fingers chomped off."

"It's almost as if this- thing- is drawn by blood. Kind of like a shark," Ryo hypothesized.

"Or a vampire," Yuki said. "Let's look at all the yōkai that crave blood."

As Yuki and Ryo searched through A History of Yōkai, two creatures stood out the most. 

"It seems our enemy may be either a rokurokubi or a nukekubi," Yuki explained. "They feed on humans, but there is a key difference between the two. The rokurokubi's neck can stretch to indefinite proportions to attack its prey. The nukekubi, however, can detach its head from its body." 

"Man... how do you stop this damn thing, whatever it is?" Ryo asked, unsettled.

"The body itself is the weak point, especially when the creature is in action. You kill the body- you kill the yōkai."

"Sounds easier said than done."

At that moment, things went from bad to worse- the power cut out.