What is this Japanese decision making game?

i was watching nobuta wo produce, and Shuuji had to pick between water and flowers. What he did was make a little diagram with four vertical lines that were in some places connected by horizontal lines. At the bottom of each line there were the options: flower, water, flower, water.



Then I'm not sure how he did it but he made his pencil trace the lines..



I just want to know what this is called, how to do it, and what's the logic behind it.

What is this Japanese decision making game?
It's called "amidakuji" in Japanese.

It's a method to distribute or decide things among people.



For more information please see the website below.

http://en.wikipedia.org/wiki/Amidakuji