Lion is a member of the Ushiromiya family who exists only within the alternate world shown in Requiem of the Golden Witch as a result of Natsuhi deciding to keep the baby Kinzo offered her. As the first child of Krauss and Natsuhi in this world, Lion is the heir to the Ushiromiya family and well-liked by the rest of the family, including Kinzo, in part because of Lion's soft-spoken nature and good-mannered upbringing. Lion becomes Willard H. Wright's partner during his investigation of Beatrice's death, becoming close with him and even leading to a running gag in which Lion would pinch Will's buttocks whenever Will acts in an disrespectful manner. Lion is given an androgynous appearance to hide their true gender.

Spoiler

Lion is in fact Kinzo's biological child together with his daughter Beatrice, and is also Yasu in another world.