じゃんけんとパジャマで遊ぶ短いイントロ

What does “janken” mean in Japanese?

じゃんけん (janken) is Japanese rock-paper-scissors, and it’s not just for kids — adults use it constantly to settle who pays, who goes first, or who gets the last piece. The three hands are グー (rock, a fist), チョキ (scissors, two fingers), and パー (paper, an open hand), and you throw them on the chant 「じゃんけん、ぽん！」.

If it’s a tie, you call 「あいこでしょ！」 (“it’s a draw!”) and throw again. The word’s exact origin is uncertain — it most likely comes from older 拳 (ken) hand-games brought over from China — but the useful part is the loop: グー beats チョキ, チョキ beats パー, パー beats グー. Knowing janken means you can join in the very first time it happens.