Sou Hiyori, whose real name is Shin Tsukimi, resists simple classification as either hero or villain, which is a large part of why fans are so captivated by him. He manipulates, deceives, and prioritises his own survival, yet the game grants him enough backstory and complexity that many players find themselves sympathising with him despite his actions. Whether he counts as a villain depends heavily on the player's interpretation and the route they pursue. The real Sou Hiyori, known as Midori, is more straightforwardly antagonistic: a sadistic floor master who torments participants purely for amusement. Together, the two characters represent very different shades of moral complexity within the same story.

Shin Tsukimi adopted the name Sou Hiyori as a deliberate survival strategy after learning in his First Trial that his odds of surviving the death game were essentially zero. Psychologically cornered, he discarded his own identity and borrowed the name of an acquaintance from his past who was believed to be dead. By disguising himself as the mild-mannered job-hopper Sou Hiyori, Shin was able to deflect suspicion and operate as an undetected strategist. The name itself carries irony: Sou is an anagram for "uso," the Japanese word for lie, while Shin's own name means truth. The Shin Tsukimi plush and Hiyori plush both capture different facets of this layered identity.

Midori is the real Sou Hiyori, the original owner of the name that Shin Tsukimi later borrowed. He has bright green hair and wide jade eyes, a striking contrast to the pale, teal-haired persona Shin presents in the death game. Midori attended the same high school as Shin and had a close, if deeply unsettling, relationship with him before the events of the game. He served as an undercover agent and was involved in manipulating Shin into signing the consent form that led to his participation in the death game. Within the game itself, Midori acts as the Floor Master of the fourth and fifth floors, functioning as a sadistic antagonist who evades players and sets traps for his own entertainment. The Midori plush and Tsukimi plush together represent both ends of this twisted relationship.

The fate of Sou Hiyori (Shin Tsukimi) is one of the most emotionally charged moments in the game and is entirely dependent on the player's choices. The second main game vote is pivotal: players can choose to sacrifice Shin or allow him to survive, leading to two distinctly different story routes. In the route where Shin lives, his character development and relationship with Kanna continues to unfold, revealing a much softer and more selfless side beneath the survival instincts. This branching possibility is a significant reason why the Shin plush carries such emotional weight for fans who have completed multiple playthroughs and grown attached to both outcomes.

The visual novel featuring Sou Hiyori, Shin Tsukimi, and Midori has been in serialised development since 2017, released in chapters by its solo developer. The fandom has remained deeply engaged throughout this time, keeping discussions, fan art, theories, and content alive between updates. For the most current information on chapter releases and development progress, checking the developer's official channels is recommended. This ongoing story is a large part of why collector items like the Sou plush and Midori plush remain so meaningful to the community, representing characters whose full arcs are still being written.