rock-paper-scissors (game); janken
じゃん拳で誰が最初にやるか決めよう。
Let's decide who goes first with rock-paper-scissors.
子供たちがじゃん拳で遊んでいた。
The children were playing rock-paper-scissors.
最後の一個をじゃんけんで取り合った。
We played rock-paper-scissors over the last one.