Shin Tsukimi

He is often classified as an INTP on the MBTI: logical, enjoys understanding systems, is prone to doubt and verify everything, and displays emotions with restraint. On the Enneagram, he is often classified as a Type 6 (Loyalist) with a wing of 5: strong anxiety, a need for security, a tendency to calculate risks, and rely on knowledge as a defense.

With Kanna Kizuchi. They're brother and sister, and Kanna clearly tries to protect him and keep him close. She even sleeps in the same room with him to keep an eye on him. Shin notices this, but doesn't always respond openly: he may manipulate her for his own safety. However, if Kanna dies, his reaction becomes very strong—he literally flies into a rage and threatens those who voted for her.
With Sarah Chidoin. He has a complex relationship with Sarah: on the one hand, he collaborates with her and recognizes her ability to lead the group, but on the other, he finds it difficult to see how easily she gains trust. This makes him envious and irritated, and at times he views her with great suspicion.
With the other participants, he keeps his distance, not trying to become everyone's "one of the gang." His strategy is to be useful just enough to remain needed, without revealing too much about himself.

Hacking is his main asset. He's skilled at working with technology, breaking into systems, searching for data, and reading logs. In the game, he regularly rummages through the devices he finds, trying to crack passwords and extract useful information.
Working with the laptop and the hidden room. One of the key plot points is when he finds the laptop and figures out the password ("Chidoin") to access the emails. This directly impacts how he begins to treat Sarah and the other participants.
Data analysis and suspicion. Due to his mentality, he doesn't take anyone's word for it and tries to double-check everything. He's often the one who points out inconsistencies in testimony and helps the team move forward with the investigation.

Shin takes the name Sou Hiyori for a reason: the situation in the Death Game weighs so heavily on him that he literally abandons his previous identity. At some point, he feels safer being "Sou"—a person who doesn't reveal too much, acts prudently, and doesn't allow himself to become attached. It's a defense mechanism: it makes it easier for him to prioritize survival.
He was kidnapped on his way to his part-time job at a convenience store in a rough neighborhood. The last thing he remembers is walking to his shift, then waking up in the Black Room on the second floor. It was there that he first learned the rules of the game and how slim his chances were: he was told his survival rate was almost zero, and this took a heavy toll on his psyche.

Shin Tsukimi is Kanna Kizuchi's older brother. Their relationship in the game is complicated: Kanna tries to look after him and even sleeps in the same room to be close, while Shin, despite his concern, continues to prioritize his own survival and may deceive her.

At first glance, Sou seems friendly, but he is reserved and distrustful. He tends to make negative judgments about people, especially Sara Chidoin, whom he envies for her ability to easily gain trust. At the same time, he helps others understand their situation and tries to find a way out.

Age: approximately 21–22 years old.
Height: 168 cm.
Hair: light turquoise, fluffy.
Eyes: dark turquoise.
Clothes: Green hat, pale brown long-sleeved shirt, khaki pants, purple jacket, pink and orange polka-dot scarf, light brown boots.
He also wears a collar, like all the other participants in the game.

Shin is one of 20 participants in the death game. He initially introduces himself as Sou Hiyori: a timid, slightly clumsy man, yet intelligent and cunning. He is a skilled hacker, a skill that plays a role in the plot several times.