Red Star Against the World

A hundred years after the beast calamity, humanity relies on the Red Star barrier to retreat into three cities. The upper city monopolizes cultivation resources, while the lower city struggles to survive, with class barriers unbreakable. After transmigrating to this world for eighteen years, Liu Hongxing has mediocre talent. His parents exhaust all means to send him to the [Apocalypse Warrior Academy], but his class is rated the lowest F-grade, and his long-term relationship ends due to a middle city residence permit. On a wilderness train back to the lower city, they are suddenly attacked by a third-tier beast. Liu Hongxing instinctively shields a stranger's child, and is swallowed by the beast in the fight. In desperation, he awakens a special power to absorb emotions like joy, anger, and compassion to temper his martial arts. After narrowly escaping, he accidentally uncovers the conspiracy of noble families deliberately triggering beast tides to plunder beast origins at the expense of lower-class lives. Surrounded by powerful enemies, he hides his edge, bides his time, with Red Star as his original aspiration and the emotions of all beings as his fuel, step by step breaking the shackles in the dark wasteland, protecting the lower class, and forging a path of resistance for the people of the lower city. — Description from novelcodex.org