Ken's apartment measured barely seventy square meters—two bedrooms and a living room. The balcony was modest as well, even narrow by most standards.
Its saving grace was the view. With neighboring high-rises set far apart, his line of sight stretched unobstructed to distant mountain ridges.
Ken did not bother dragging a chair outside. Instead, he lay down directly on the balcony's ceramic tiles—cleaned thoroughly beforehand, of course.
Under the veil of night, he felt exceptionally well. His bodily functions had reached their peak, and after three consecutive blood-feedings paired with targeted training, his sensory faculties had undergone mutation and evolution, improving by a considerable margin.
Unfortunately, limited by equipment and methodology, he had no way to conduct precise measurements or collect reliable statistics. He had once downloaded an app capable of emitting sounds from 1 to 22,000 hertz, but that only tested the range of frequencies he could perceive—it offered no comprehensive measure of the overall enhancement to his hearing. He had also experimented with fixed sound sources, increasing distance to determine the farthest range at which he could still hear them. Yet such methods required stable, controlled environments, were easily disrupted, and yielded imprecise results.
His sense of smell was much the same—only rough, subjective testing was possible.
Lying flat on the balcony tiles, Ken closed his eyes, relaxed his muscles, and focused all his attention on his hearing and sense of smell—primary hearing, secondary olfaction.
In an instant, sound surged toward him like floodwaters released from a dam, countless layers of noise colliding and overlapping. Scents followed suit, blooming and intertwining in the air.
The human brain processes external information through a highly refined mechanism—one might call it a protective system, or just as aptly, a mechanism of efficiency.
When attention is not directed toward sound or smell, the auditory and olfactory organs still collect information, but the brain attenuates, filters, or even blocks much of it.
Conversely, when attention is deliberately focused on sound or scent, the brain can amplify and prioritize relevant signals, suppressing interference from others.
Yet perceiving a sound or scent, locking onto a sensory input, is one thing. Interpreting that information and drawing conclusions from it is quite another.
Consider someone sitting at home who hears a car roar past outside.
If the sound catches his attention, an image will instinctively form in his mind: a vehicle speeding along the road beyond his window.
That image arises because he is familiar with the road outside, has heard cars before, and has seen them rush past along that very street.
Someone even more familiar with engines and exhaust notes might go further—identifying whether the car has a four-cylinder or six-cylinder engine, whether it's a Ford or a Toyota, whether it's a battered diesel truck or a supercar. The mental image grows correspondingly vivid and detailed.
Likewise, if that same person hears crisp, rhythmic footsteps above—tap, tap, tap—he will recognize the sound as high heels. If he has never seen the upstairs resident, his mind might conjure the image of a young woman with long legs pacing back and forth. But if he knows the resident is a fifty-year-old auntie, then the very same sound will instead evoke her image walking across the floor.
The brain fills in the blanks according to its internal "database"—experience, logic, memory, and instinct.
Thus, collecting sensory information is one thing. Whether that information can truly be useful, whether it can aid the brain in making accurate judgments, is another matter entirely.
Ken lay directly on the floor not because he lacked a chair or a blanket, but because in reinforced concrete buildings like this, aside from air, walls and floors are the primary conduits for sound transmission. By lying flat and making direct contact with the ground, he could more easily perceive the sounds coursing through the entire building.
Amid the cacophony, Ken carefully distinguished and filtered, starting with the closest sounds.
Directly below, from apartment 608, he discerned the voices of what sounded like a middle-aged couple discussing their son, who had gone north for university. In the background, the television played the evening news.
To one side, the neighboring unit was silent—no footsteps, no appliances, no voices, not even breathing. Yet he heard the faint rustle of curtains stirred by airflow. The windows were likely open, the residents absent.
Then he caught the familiar voice of Liu Shiling, the chubby little girl he had met earlier that day, and located her in apartment 706—he knew her family lived there.
From the sounds alone, he judged that Shiling and her mother were home. Her mother was urging her to go take a bath, while Shiling stubbornly clung to the television, unwilling to abandon her cartoon.
Using 706 as a reference point, Ken continued to map the building through sound, drawing conclusions as he went.
When he heard footsteps, he could infer not only where someone was inside their apartment, but even the direction in which they were moving—using the structure of his own home as a template, along with reference sounds such as running water, the click of a gas stove igniting, cups being lifted, or appliances switching on.
Smell served as a secondary aid. When he heard the clatter of a wok and spatula and the hiss of stir-frying from apartment 402, the accompanying aromas allowed him to identify the dish being cooked—and even guess the flavor profile with fair accuracy.
Sound and scent cross-validated each other, enabling far more precise spatial localization.
Time passed little by little. From outside, the lights across the residential complex gradually winked out, and the sounds of daily life softened into quiet.
It was past one in the morning when Ken finally opened his eyes, sat up, and stretched.
Using sound and scent, he had "walked through" the entire building—every household, every unit. Though the only person he had actually met and spoken to by name was little Liu Shiling from 706, over the course of the night he had, in a sense, come to know almost everyone in the building, even uncovering a fair number of private secrets.
Of course, Ken had no interest in prying into others' privacy. This was training.
Just as he had shifted to training endurance and agility after increasing his muscle mass, the rapid growth of his sensory abilities now demanded that he train his brain's capacity to process and apply the information they provided.
It was like two professional athletes of similar weight and muscle mass: because they trained for different sports, their force application differed, and so did the results. A professional boxer's punch would naturally carry more impact than a professional basketball player's, while the basketball player, under the same level of physical contact, would execute basketball maneuvers far more effectively than the boxer.
Ken understood this principle clearly. Enhanced senses alone were not enough. He needed practice—he needed to learn how to wield these formidable faculties.
The first stage had been the collection of previously inaccessible "samples" of sound and scent, building a mental database and embedding it into instinct. That phase was largely complete.
The second stage was what he was doing now: using sound and scent to assess his surroundings, turning them into his "super eyes."
Though it currently took him five or six hours to survey an entire building, once fully familiar, it might take only a second or two to pinpoint anyone's exact location through sound and smell alone—perhaps even constructing a real-time, holographic map of the entire structure within his mind.
Ken had already noticed that as his sensory abilities evolved, so too did his brain. At the very least, immersing himself simultaneously in multiple layers of sound no longer induced the nausea and dizziness he had experienced at the beginning.
The next morning at seven-thirty, Ken slung his sports bag over his shoulder and headed out for the gym.
Although the gym was far from his current apartment—requiring a subway ride and a bus transfer, taking at least forty to fifty minutes—he had no intention of switching locations. He had already paid for the membership, after all, and refunds were not an option.
Besides, he wasn't planning to take public transportation anyway. He intended to run there. The journey itself would serve as training.
As he stepped outside, he happened to see Liu Shiling from 706 heading out as well. Behind her was a curvy woman who resembled her by sixty or seventy percent—presumably her mother.
"Bald Uncle!" Shiling called out the moment she spotted Ken, scampering over.
Her mother immediately looked embarrassed and hurried forward. "Oh, I'm so sorry. She's just a child—she doesn't know any better and calls people whatever comes to mind. You're the new tenant in 708, right? We'll be neighbors from now on. If you ever need anything, don't hesitate to ask."
Shiling ran ahead to press the elevator button, while Ken chatted briefly with her mother. He learned that they had moved into 706 earlier that year and had purchased the apartment. Shiling's father worked in construction and was often away, while her mother was a full-time homemaker, devoted primarily to their only child.
Ken gave a brief introduction of his own, saying he was a programmer with seven years of experience—omitting the detail that he was currently unemployed.
They didn't have to wait long. The building had two elevators per unit, and one soon arrived.
With a chime, the doors slid open—only for a dog's head to thrust out aggressively, lunging forward. Liu Shiling, standing at the doorway ready to step in, was startled and stumbled back two steps, nearly falling. Ken reacted instantly, steadying her.
Looking inside, he saw a young woman in her twenties holding the leash of a fully grown husky. The dog was visibly overexcited, straining to leap out the moment the doors opened. The woman, distracted by her phone, almost lost her grip.
"PINKIE! PINKIE! STOP! Don't move!" she shouted, grabbing the leash with both hands.
The husky continued to struggle, while the little girl outside was clearly terrified, clutching Ken's leg and too frightened to speak.
Shiling's mother evidently knew the woman and frowned. "Miss Yang, please keep your dog under control. This elevator is so small, the dog is so big, and the child is so little—what if she gets bitten or knocked over?"
Miss Yang tugged at the leash without even lifting her head. "It's fine. Pinkie just wants to play with the kid. She won't bite. I've got her… PINKIE! STOP! SIT! SIT!"
This was clearly not the first time Shiling's mother had raised the issue, and she knew it was useless. She pressed the elevator button again and said to Ken, "You go ahead. We'll take the next one."
Ken, however, took the little girl's hand and walked into the elevator with her.
Shiling was still hesitant at first, but then she noticed something strange—the husky, which moments earlier had been wildly lunging despite its owner's efforts, had now shrunk back behind Miss Yang. Its head pressed against the elevator wall, its body trembling.
Ken turned back and said calmly to Shiling's mother, "It's fine. Come in together."