A young man lives an ordinary life, but every now and then, he has an existential experience that is entirely and uniquely his own. No matter how hard he tries to get others to relate to it, imagine it, interpret it, no one, not even the greatest psychologists like Carl Jung can explain just how beyond simple "introverted intuition" this experience is, and so it cannot be measured for it is separate from universal human experience.
Dealing with this aspect of his life that he is aware of that is mostly out of his control, he explores the ideas that come from this alternate non-human experience he has from the lens of a human's intellect, and comes to gain some level of gradual, conscious control over this capability.
Whenever he goes to sleep, he has a dream continued from the night previously, but he would always forget the events of the day in the world he goes to once he wakes up, but always senses a great sense of familiarity and the spiritual "tag" of anything that comes from this other world whenever he happens to walk past it in the waking world.
For example, an ordinary tree can be associated with many things, but a pure child would experience the presence of the tree, whereas the young man experiences both the presence of the tree as well as the secret otherworld presence that is tagged to that specific tree if it comes from that other world.
Intrigued, he seeks to make sure that he is able to remember his dreams from here onwards in order to find out why the secret presence is both something he is receptive to but also has a great sense of familiarity attached to it.
...
One day, as his normal life progresses as usual despite his unique perception, while doing his job at the gas station behind the cash register, he senses the presence of a person who has a secret presence tag attached to them.
He looks up out of shock, maybe finally someone who he can relate to has coincidently entered the gas station?
He sees no one.
However, the presence is so clear to him even with his eyes closed that he begins to move around and pinpoints the exact location of the person.
Whoever it is, they're completely invisible, or maybe immaterial, and appears to be floating off of the ground if they are there.
"Hello? I know you're there.", the person doesn't move, and as he assumes this person is observing the situation around themselves, he gets a chair out at the front entrance of the gas station indoors, and decides to sit there and observe the presence as he waits for this real but non-physical person to do something.
Someone walks through the sliding door of the gas station, wondering why the employee is just staring with a very concentrated face at the door, and they proceed to unknowingly walk through the floating otherworldly person.
The moment this happens, the otherworldly person moves quickly in the direction of the young man who senses them, and he ducks instinctively as they phase through the shelves and spinning around as if doing summersaults.