Does Sasaki Know Tayama Is Yamada?
Yes. Sasaki eventually realizes Tayama is Yamada in Smoking Behind the Supermarket with You, but he chooses not to force her to reveal the truth.
First, this is a different manga from The Guy She Was Interested in Wasn't a Guy at All
The premise in the requested franchise label mixes together two separate series.
Sumiko Arai's The Guy She Was Interested in Wasn't a Guy at All centers on high school classmates Aya Oosawa and Mitsuki Koga. Aya becomes interested in a stylish employee at a CD shop without realizing that the apparently male clerk is Mitsuki, the girl who sits near her at school. Its identity misunderstanding therefore involves Aya and Mitsuki.
Sasaki, Yamada, and Tayama instead come from Smoking Behind the Supermarket with You, a manga by Jinushi published by Square Enix. Because the question "Does Sasaki know Tayama is Yamada?" only makes sense in that story, the canon explanation below follows Smoking Behind the Supermarket with You rather than forcing those names into an unrelated series.
Yamada and Tayama are the same person from the beginning
There is no late twist for the reader: Yamada and Tayama are one woman.
Sasaki is an exhausted middle-aged office worker whose small daily comforts include cigarettes and the warm customer service of Yamada, an employee at Super S. He sees "Yamada" primarily while she is working: neat, approachable, smiling, and operating in professional customer-service mode.
One evening, after missing Yamada at the register, Sasaki encounters a much more casually dressed woman behind the supermarket. She invites him to the employees' smoking area and introduces herself to him as Tayama. Her clothing, piercings, hairstyle, and off-duty demeanor make such a different impression that Sasaki fails to recognize her.
The audience is shown the truth almost immediately. "Tayama" is Yamada herself, using a false name after realizing that Sasaki has not recognized her outside work.
Yamada allows his mistake to continue, and the smoking-area relationship acquires a value of its own. Sasaki can talk to Tayama in ways he never would with the cashier he has placed on a pedestal, while Yamada gets to interact with him without the expectations attached to her workplace persona.
That visual contrast is the key image for the early story: Sasaki sees the bright uniformed cashier at the register and the pierced, off-duty smoking companion behind the store as two different women, while the reader can plainly see that both are Yamada.
What Sasaki knows during the early manga
For a large part of the series, Sasaki does not secretly know the truth.
The manga's initial comedy genuinely depends on his failure to connect the two identities. Sasaki believes Yamada and Tayama are separate coworkers who know each other. Because he talks about Yamada while sitting beside Tayama, Yamada hears exactly how he thinks about her when he believes she is absent.
His admiration is sincere but restrained. Yamada's kindness and smile help him endure difficult workdays, and Sasaki is conscious of not wanting to turn that appreciation into something invasive. He largely regards himself as an ordinary customer grateful for a small source of encouragement.
At the same time, he becomes attached to Tayama independently. Their cigarettes behind the supermarket turn into a recurring refuge in his routine. She teases him, challenges him, listens to him, and sometimes supports him when he is exhausted or discouraged.
Sasaki consequently develops two emotional impressions of what he believes are two women. "Yamada"is someone he admires from a respectful distance."Tayama" is someone with whom he can be awkward, candid, irritated, amused, and vulnerable.
Yamada experiences both sides. That is why the false identity eventually stops being a simple prank. Revealing herself means exposing the fact that she has heard Sasaki talk about her while he thought he was speaking privately to somebody else.
When Sasaki starts realizing Tayama is Yamada
The decisive shift occurs in Volume 7.
By this stage, the manga has spent enough time showing Sasaki both versions of Yamada that their similarities become increasingly difficult for him to dismiss. Interactions involving Tayama, Yamada, and the people around them push him toward a question he once seemed almost incapable of asking.
Square Enix's official description of Volume 7 deliberately frames this period as one in which events surrounding Tayama give Sasaki an unexpected realization and growing doubts about "Yamada and Tayama." Inside the volume, his thoughts make the direction of that suspicion unmistakable: he begins seriously considering whether the two women are actually the same person.
That is the important reveal timing. Volume 7 is where Sasaki's ignorance breaks down. It is more precise to say that he reaches the truth through observation and accumulated evidence than to describe the moment as Yamada confessing her identity.
Sasaki processes what he has noticed rather than immediately turning one clue into a confrontation. That fits his personality. He is cautious, often self-effacing, and intensely reluctant to intrude into another person's private circumstances.
By the transition into the next stage of the story, the question is no longer whether Sasaki is capable of noticing. It is what he will do now that he understands.
Yamada does not simply confess, and Sasaki chooses to wait
The identity storyline becomes especially revealing after Tayama goes missing during the events surrounding the end of Volume 7 and the beginning of Volume 8.
Sasaki's response confirms how much his understanding has changed. He learns more about the reason behind Yamada's long-running "Tayama" lie and, crucially, does not demand an immediate explanation from her.
Volume 8's official synopsis describes him as learning the intention behind her lie and choosing to wait for her. That is the clearest way to summarize his position: Sasaki knows, but he does not want to take the act of revealing herself away from Yamada.
He even asks another person not to tell her yet that he has figured it out. That choice is not another layer of cluelessness. It is conscious restraint.
Early in the manga, Yamada knows something Sasaki does not. After Sasaki works out the truth, the imbalance changes: he now understands the central secret while Yamada does not necessarily know exactly how much he has pieced together.
For an illustrator, the mood should therefore be completely different from the early split-image joke. Sasaki and off-duty Yamada are sitting together in the familiar smoking area, but his expression now carries recognition rather than confusion. He sees Yamada when he looks at "Tayama," yet chooses not to corner her with that knowledge.
Why Sasaki keeping quiet matters to their relationship
Once he knows, the identity issue becomes a question of trust rather than detection.
Yamada has reasons for maintaining the divide between her professional "Yamada" presentation and the more unguarded person Sasaki knows as Tayama. What began as a false identity became emotionally meaningful because it gave her a relationship with Sasaki that was not dependent on his admiration for the smiling cashier.
Sasaki recognizes that forcing the issue could reduce everything they have built to a gotcha moment: he discovered the disguise, so she must explain herself immediately. Instead, he gives her room to decide when she is prepared to collapse the two identities in front of him.
Before the realization, Sasaki can compartmentalize Yamada as an admired source of comfort and Tayama as the person with whom he shares quiet, increasingly intimate evenings. Once he knows they are one woman, those emotional categories can no longer remain cleanly separated.
Awareness therefore creates a new kind of awkwardness rather than instantly solving the romance. Sasaki has to reinterpret his accumulated impressions, while Yamada has to confront what she wants their bond to become when she can no longer rely indefinitely on the protective distance of the Tayama name.
This is also why saying that the identity "gets revealed" can be misleading. The factual mystery is resolved for Sasaki, but the emotional act of Yamada openly presenting both sides of herself to him is a separate matter.
Knowing the truth does not mean they immediately become a couple
It would be inaccurate to turn the identity reveal into a romantic confession that the manga has not given.
By the latest collected Japanese material available as of August 16, 2026, Volume 9, Sasaki knowing Yamada and Tayama are the same person is established territory. Their story has moved beyond the original "will he notice?" setup and into questions about work, personal ambitions, emotional honesty, and what their relationship can become.
Volume 9's official description emphasizes both characters moving forward in their own lives. Yamada opens up to Sasaki about a dream she had once abandoned and decides to face it again, while Sasaki achieves an important result on a business trip and has to confront recognition at his own workplace. Their increasing emotional closeness accompanies those individual changes.
What canon does not justify is inventing a scene where Yamada formally reveals the identity, Sasaki immediately confesses his love, and the two establish a conventional relationship on the spot. The manga's progression is quieter and intentionally less mechanical than that.
Resolving factual knowledge and defining a romance are two different milestones. Sasaki can know who she is while both characters still have to determine how much of themselves they are ready to expose and what their unusual bond means.
The important relationship development is therefore not simply that Sasaki solves the puzzle. It is that knowing the truth does not make him treat Yamada's vulnerability as something he has earned the right to demand.
What the anime currently knows versus the manga
The 2026 TV anime is much earlier in the story than the manga's Volume 7 identity development.
As of August 16, 2026, the official anime site lists six aired story installments. At that point, the adaptation is still operating within the original premise: viewers know Yamada and Tayama are the same woman, while Sasaki treats them as separate people.
That means an anime-only viewer asking this question currently gets a different answer from a manga reader. Anime Sasaki does not yet know. Manga Sasaki does.
The television series is officially planned for 12 episodes, but there is no official confirmation that this season will reach the manga's Volume 7 realization. Claiming that a particular upcoming episode will contain Sasaki discovering the truth would therefore be prediction rather than confirmed adaptation information.
There is also no separate light-novel or web-novel continuity governing the reveal. Smoking Behind the Supermarket with You is fundamentally a manga series, with the television anime adapting Jinushi's work. No film continuity changes Sasaki's knowledge either.
So the current canon answer depends on where someone is following the story: Sasaki spends the early material genuinely fooled, realizes the truth around Volume 7, and by Volume 8 consciously chooses not to force Yamada to admit it before she is ready. The identity misunderstanding begins as one of the manga's central jokes, but its resolution becomes something more character-driven: a demonstration that recognizing someone and giving them space to show themselves are not necessarily the same thing.