Reiko has been a teacher for many years and takes pride in having successfully graduated all of her students, without a single missing. Thanks to her dedicated teaching, this year all of her students were able to attend their graduation ceremony in style. At dusk, in an empty classroom, messages of gratitude from the students are written on the blackboard... As Reiko looks around the classroom with deep emotion, the four troublesome children who have been giving her so much trouble open the classroom door with gusto and approach her, saying, "We want to thank all the teachers who have helped us so much."