Also known as "Insignificant Dumble" and "Unlucky Dumble"
Harry Potter fanfic, unorthodox first-person lazy style, with many interesting anecdotes, set 17 years after the war (2015)
Before and after time travel, the protagonist is an ordinary and inconspicuous Muggle-born boy. He has no profound magical background, no magical talent for being self-taught, and has no understanding of the magical world. He is sincere, simple, and law-abiding.
Such a child was accidentally placed in the "Problem Child Control Center" as a temporary replacement...
"Sorry, it turns out that child just decided to transfer to another school a few days ago, so we had no choice but to find a fool to support him," the vice principal said.
"... OTZ"
Spoiler site→←Caution