Hidden in High School, Why Did the Green Plum from the Sky Come After Me?

[Genius flow + semi-group portrait + slow heat + no system + single female protagonist It's not a brainless novel, the heroine will appear in Chapter 16] In the age of global martial arts, spiritual civilization is in full bloom. Daxia monk, Western mage, federal superpower, neon onmyoji... The era of psychic technology has connected the world's major spiritual civilizations together. Countries are working together to fight against the "Black Tide" disaster, but secretly there is an undercurrent. Lin Yan, the proud son of the Demon Slaying Division of Dongsheng Prefecture in Daxia, is sixteen years old and has top-notch qualifications with ten years of combat experience! After three years of fighting on the front line, a piece of intelligence led him to the rear where he had never been. The mastermind behind the human experiment that included him in the "Ascension Project", there were actually remnants of the "Sky Demon Sect" lurking. Clues point to Amagi High School, where a new conspiracy is brewing. Whether he was a member of the Demon Slaying Division or the "Nine Violent Sons" who had merged with the origin of the [Shadowless Wind] demonic beasts, Lin Yan was ready to kill them all. In order to catch all the remnants, Lin Yan put on his school uniform and sneaked into the campus as a freshman in high school. However, on his first day at Daxia High School, he discovered a serious oversight in his plan. Lin Yan, a real person who slipped through the nine-year compulsory education, has a serious father-in-law who has never been to school! In order to prevent his work from collapsing into his studies, his boss forced him to find an extracurricular tutor. And when Lin Yan returned to his residence at night and saw that familiar figure, his pupils could not help but shrink... The "teacher" who came to give him tutoring was actually his former "green plum" whom he hadn't seen for four years?