With the latest released episodes of Spy x Family, Yuri Briar seems to be completely clueless about Yor Forger’s real identity, despite being the closest person to his older sister in the anime series.
As evident in the 8th and 9th episodes on a flashback, where Yor returns home with her face and clothing covered in blood. Despite the shocking state of his sister, Yuri doesn’t appear to show an extreme level of suspicion about her occupation or the reason for the blood on her body. Instead, his emotions become irrational and overpowered when Yor presents him with a gift or changes the topic of their conversation.

What Is Briar’s Tragic Backstory?
Following the death of their parents, Yor Forger assumed the responsibility of raising her younger sibling. With no one to depend on, the orphans initially endured a life of poverty as they endeavored to cope and fulfill their daily requirements. Recognizing that their impoverished state was not sustainable, Yor resolved to join the Garden, an assassin organization operating in Ostania.
Yor kept her affiliation with the Garden a secret, willingly sacrificing her own future to secure a better life for her younger brother. We can say that her childhood was quite painful, as she was trained to become a lethal weapon. She was also exposed to harsh environments and dangerous situations during her missions as an assassin.

Why Did Yor Become an Assassin?
Nevertheless, she persevered and put in a lot of effort while approaching her work with utmost seriousness. Considering that regular life is out of the question for Yor, she desires a prosperous future for her younger sibling. Yor wishes for him to complete his education and thrive in life away from danger.
In order to achieve this goal, Yor persisted in her role as an assassin within the organization, taking on countless assignments and eliminating numerous targets. Her unwavering determination paid off as she eventually rose to the position of one of the top assassins in the organization, earning the moniker “Thorn Princess” without ever revealing her true identity to her brother.

What Is “The Garden” in Spy x Family?
“The Garden” is an unacknowledged paramilitary organization that carries out the execution of traitors to the country upon orders from the shadow government. While the organization’s intentions remain ambiguous, as it maintains links to criminal activities, it is essential to note that its killings target only those deemed undesirable to the nation. Therefore, a sense of moral ambiguity exists around the Garden, with some regarding their actions as justifiable, while others perceive them as detrimental.
Who Is Yuri Briar?
In the second episode of the anime Spy x Family, titled “Secure a Wife,” Yuri Briar made his debut by contacting Yor on the phone in the evening. During the conversation, he inquired about her personal life, asking for updates on her well-being, romantic prospects, and any potential love interests that may have caught her attention.
Yuri expressed his heartfelt concern for his older sister, remarking that Yor is a peculiar individual. He reiterated his desire to repay his sister’s hard work by looking out for him, acknowledging that he would not be the person he is today without her. To that end, Yuri vowed to go to great lengths to ensure that Yor could lead a happy life, as he believed that she deserved nothing but the best.
Read more: 5 Interesting Facts About Yuri Briar in Spy x Family

Following that, Yuri informed Yor about a job promotion he had received, expressing reservations about accepting it due to the increased workload that would make it more challenging for them to keep in touch. He then offered to introduce someone to Yor, but she declined, instead informing him that she would attend a party the following week with a date.
Yuri proceeded to declare that he would delay accepting the job promotion until he had ensured that the man Yor planned to go to the party with was suitable, worthy of his sister, and harbored no ulterior motives. The exchange between the siblings culminated in a chaotic argument, as Yor had lied to her younger brother since she had no one to accompany her to the event.

What Is “The Secret Police” or State Security Service (SSS) In Spy X Family?
Initially portrayed as an endearing young boy who had an intense admiration for his elder sister, Yuri’s character took an unexpected turn in episode eight. It was revealed that he was working as a “Secret Police” officer under the National Security Agency.
The State Security Service, commonly known as the “Secret Police,” is an organization created in Ostania to safeguard domestic stability. The primary mission of this institution is to detect and apprehend spies and monitor the general population’s activities. Thus, WISE‘s rival.
The methods employed by the Secret Police are quite unscrupulous. As a result, the public views the Secret Police with apprehension, as they are deemed an oppressive force. Their brutal and inhumane tactics have led to widespread fear and mistrust among the people.

What Does Yuri Do as a Secret Police Officer?
Later on, In the 8th episode of Spy x Family, entitled “The Counter-Secret Police Cover Operation,” we get to know more information about Yuri Briar as he makes his first appearance in the anime series.
Yuri holds the rank of second lieutenant within the National Security Agency and is responsible for various activities such as assault, wiretapping, intimidation, and torture to extract vital information from suspected terrorists.
In the same episode, we saw him interrogate a man named Mr. Hayward, who coincidentally works in the same city hall as his older sister. Yuri has shown great skills in his profession as he handled the case seriously and prepared with evidence to let the suspect know that he could find out the truth.
Yuri mentioned that he concealed his position as a Secret Police officer from his older sister because he did not want her to be anxious about his involvement in illicit operations. Like his sister, Yuri is also in a façade to put his other siblings at ease.

Why is Yuri unaware that Yor is an assassin?
Ultimately, Yuri is completely unaware of Yor’s involvement in “The Garden.” Even though Yuri is highly proficient in his role as a Secret Police officer, his abilities in gathering information and obtaining evidence do not extend to his sister’s secretive activities.
Yuri seems to undergo a significant change in behavior when interacting with his sister, as if he is under a spell that prevents him from seeing any negative aspects of her. Despite his exceptional abilities in the SSS, he appears to be clueless when it comes to his sister’s involvement in a dangerous group of assassins. It’s almost as if his judgment is clouded by his affection for his sister, making him oblivious to any suspicious or unusual activity surrounding her.

As evident in the 18th episode of the anime series, Yor asked Yuri to tutor Anya for her upcoming exam. Initially, he refuses to teach Anya since he is the daughter of Loid Forger, whom he thinks of as his rival because he is “the man who stole his sister from him.”
Despite hating and refusing to help Anya, Yuri eventually agreed to teach Anya when Yor requested it, saying she was counting on his little brother to help Anya pass the test, knowing that his sister was counting on him to assist Anya in passing the exam. This made Yuri overjoyed since it was an opportunity to make Yor happy, which is what both of them want for each other, to make each other happy despite living the same conditions in life, as one being an assassin and one being a Secret Police officer.