You need a set of maru-batsu paddles for each student.
Before the game begins, tell the students that batsu is “ODD” and maru is “EVEN”. Confirm that the students know what these words mean.
Students should make fists with both their hands and rest them on the table, thumb side up. Have everyone pound on the table together to the count of three. On three, everyone should raise either one or both of their thumbs, and the total number of thumbs raised is counted.
Each round, students will need to correctly guess whether the total number of thumbs up will be odd or even. They should indicate their choice by placing their maru-batsu paddle face-up on the table showing the “ODD” side or the “EVEN” side. If they guess correctly, they continue to the next round. If they are incorrect, they are eliminated. The final student remaining is the winner and receives five points.
If there are only two students in the class, the teacher should play too. In the event there are only two people remaining in a round, the teacher should decide who is “ODD” and who is “EVEN”.
VARIATION: Everyone has three lives. Use fluffy balls or some other kind of counter to represent lives. One by one around the circle, students take it in turns guessing “ODD” or “EVEN”. Whenever someone incorrectly guesses the number of thumbs up, they lose a life. Keep playing until all but one student has run out of lives.