“That makes sense,” Tsukuru said. “I get the feeling it’s connected with the process of how the world’s counting systems have mainly standardized, moving from the duodecimal system to the decimal system.”

“Yes, that might have been a response to six and five fingers, digits, now that you mention it,” Sakamoto said.

“So how come you know so much about this?” Tsukuru asked Sakamoto.

“I took a class on genetics in college. I sort of had a personal interest in it.” Sakamoto’s cheeks reddened as he said this.

The stationmaster gave a merry laugh. “So your genetics class came in handy, even after you started work at a railway company. I guess getting an education isn’t something to be sneezed at, is it.”

Tsukuru turned to the stationmaster. “Seems like for a pianist, though, having six fingers could come in pretty handy.”

“Apparently it doesn’t,” the stationmaster replied. “One pianist who has six fingers said the extra ones get in the way. Like Mr. Sakamoto said just now, moving six fingers equally and freely might be a little too much for human beings. Maybe five is just the right number.”

“Is there some advantage to having six fingers?” Tsukuru asked.

“From what I learned,” the stationmaster replied, “during the Middle Ages in Europe, they thought people born with six fingers were magicians or witches, and they were burned at the stake. And in one country during the era of the Crusaders, anybody who had six fingers was killed. Whether these stories are true or not, I don’t know. In Borneo children born with six fingers are automatically treated as shamans. Maybe that isn’t an advantage, however.”

“Shamans?” Tsukuru asked.

“Just in Borneo.”

Lunchtime was over, and so was their conversation. Tsukuru thanked the stationmaster for the lunch, and he and Sakamoto returned to their office.

As Tsukuru was writing some notes on the blueprints, he suddenly recalled the story Haida had told him, years ago, about his father. How the jazz pianist who was staying at the inn deep in the mountains of Oita had, just before he started playing, put a cloth bag on top of the piano. Could there have been, inside the bag, a sixth right and left finger, preserved in formaldehyde inside a jar? For some reason maybe he’d waited until he was an adult to get them amputated, and always carried the jar around with him. And just before he performed he’d put them on top of the piano. Like a talisman.

Of course, this was sheer conjecture. There was no basis for it. And that incident had taken place—if indeed it had actually occurred—over forty years ago. Still, the more Tsukuru thought about it, the more it seemed like this piece of the puzzle fit the lacuna in Haida’s story. Tsukuru sat at his drafting table until evening, pencil in hand, mulling over the idea.