Masumi Nakajima 中嶋真澄（なかじま・ますみ）
Psychological test writer. Head of Enneagram Associates. Provides psychological tests, self-diagnosis tests, character analysis and logic for various devices based on unique personality research in seminars and workshops.
His books include "Psychological tests that are so interesting you'll lose track of time" (Mikasa Shobo), "Understanding true feelings that can't be told to others! Psychological tests for adults" (Ikeda Shoten), "Don't be so prickly. 64 tips for interacting with people happily!" (Graphic-sha), "Psychological tests that reveal your true self so well that it's scary" (PHP Institute), and many more. He also creates and supervises psychological tests for TV, magazines, and the web.