My Martial Arts Shrinks

Lin Ye is a well-known loser at Chengnan Middle School. While others grow stronger with martial arts training, he only shrinks. Everyone thinks he's useless. Only he knows that during high tide, his strength is more than double his usual, and during low tide, he's weaker than an ordinary person. He thinks it's a disease. Until Old Wang at the second-hand book market takes his pulse. The old man says, tidal body. The old man adds, those who don't accept it die fast. The martial arts of this world have two faces. One is in the sunlight, with a nine-rank system, martial arts college entrance exams, and universal admiration. The other is in the shadows. The deeper you train, the heavier your shadow. Until one day, you can't tell if it's you or something else that's acting. Lin Ye stands between the two faces. The more he shrinks, the clearer he sees. — Description from novelcodex.org