This colors Tsukuru's life and how he approaches people and relationships. He is forever haunted by these four friends until one day a girlfriend of his offers to find out what happened to all 4 of his friends.
She finds out that one is dead, two are still alive in his hometown and one has moved to Finland. She challenges Tsukuru to visit these friends and find out once and for all what happened 15 years ago. So Tsukuru makes the journey back home as well as to Finland to find out the big secret.
I really enjoyed this book because it told a tale that could have happened in any culture - it showed how people in all cultures were really the same underneath - they have the same concerns, loves, friendships and hard times.