Synopsis for
Vanished (2006) More at IMDbPro »Oyayubi sagashi (original title)

On a hot summer day at an elementary school reunion, Takeshi finds himself seated at the same table with his old schoolmates Chie, Tomohiko, Aya and Nobuhisa. While they haven't seen each other since graduation, at Takeshi's urging, they decide to play "the game" one more time - for Yumiko.

8 years ago, it was Yumiko who initiated "the game". With eyes closed, holding hands and forming a circle, they recite a chant that will transport their souls to another place - a room where they might find the missing thumb of a dead girl. Whoever found it would be granted their wish. But if someone tapped you on the shoulder, you must never look back or you would be trapped in the room forever.

The six classmates nervously begin the ritual, and just moments before "the game" begins, Yumiko asks Takeshi, "What would you do if I disappeared?"

"I promise I would find you."

Then Takeshi is transported to a room he has never seen before. He scrambles around in search of the missing thumb, but hears Yumiko's scream from another room. As he tries to find her, someone taps him on the shoulder. A white hand... without a thumb. In a blind panic, Takeshi returns to the real world, leaving Yumiko behind.

Yumiko is never found. Takeshi insists to the police that Yumiko disappeared playing "the game", but no one believes him and Yumiko's disappearance is filed away as a runaway case.

8 years later. The group hesitantly replays "the game", each grappling with his own guilt over Yumiko's disappearance. They join hands just as they did 8 years ago and begin the ritual, but nothing happens...

Then, inexplicably, one by one, the classmates start to disappear. Takeshi and the remaining friends begin investigating the mysterious legend behind "the game"...

Source: English-language page for the movie on Pony Canyon's website.