Strange Truth-Finding Record

The 28-year-old protagonist was killed and traveled back to 18 years old! His original life has changed because of his "rebirth". He wanted to know the cause of his death, but was told the "truth" of the world by a mysterious man. He followed the mysterious man to investigate the "truth" and crossed paths with the daughter of his murderer. He occasionally heard vague sounds, which he initially dismissed as hallucinations caused by stress. However, as the auditory hallucinations became longer and clearer, he became frightened and decided to find the source of the auditory hallucinations. After a series of events, he was shocked to discover that he had fallen into a coma at the age of 18, and that his experiences in the next ten years were just illusions. That sound was actually the nursery rhyme his mother sang to him! It turns out that the protagonist has fallen into an endless loop of coma. Every time he "wakes up", he thinks he has traveled back in time, but time in the real world is constantly passing... Can he escape this weird fate? Can we know the real world? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.