Dorami & Doraemons: Robot School's Seven Mysteries by Ryochi Yonetani

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It is time for Doraemon's younger sister - Dorami-chan to graduate from the Robot School. But a mysterious wind sucks Doraemon and the principal away. Dorami escapes, and finds Doraemon's Good Friend Telepathy Card. This is a device Doraemon uses to communicate with his friends—collectively known as The Doraemons.