The twinship and alter-ego experiences, among the most significant concepts of Heinz Kohut’s Psychology of the Self, were referred to interchangeably throughout his work. Both are defined as “an experience of essential alikeness” and/or “a sense of being human among humans.” However, the two terms are not necessarily the same. Twinship, which emphasizes the word twin, focuses on the relationship between two people who are seen as being alike, while alter-ego, the etymology of which is “alter idem” in Latin, implies a person can love another as he or she does him or herself (Togashi, 2019). Kohut neither acknowledged their different meanings nor did he explain how they related to each other. Why did he imply that the terms are the same? In what sense did he consider them the same under the definition of a sense of being human among humans? In this presentation, I attempt to clarify these questions by referring to the concept of the player-witness in the traumatized world, “Tojisha” in Japanese, which, I believe, emerges where the twinship experience and the alter-ego experience come into contact with each other. The player-witness is not a person who simply witnesses an event, but a person who knows that, under other circumstances, he or she could have taken any role, in that event or any other. I discuss how this concept represents the essential sense of being human among humans.