Toaru Majutsu no Index - Volume 17, Chapter 1: The Incongruity of Casual Conversation. Irregular_Spark.

What would you do if you could control and use your Karma?

After 20 years of dedicating his life to opera ever since he had quit the performing arts high school, he had failed at an interview. Losing his motivations, Jo Yunjae depended on alcohol to live out his days until one day, he had been sent back 20 years in time, to the day before his high school admission.

She fought in the Battle of Changping and witnessed the killing of hundreds of thousands. She once led the Qin Iron Calvary and battled against the Six Kingdoms. She has seen a third of the land and witnessed the breaking of mountains and rivers. The sound of a grand zither and the light of a great female emperor. A prosperous world that was forged on the battlefield. Yet, these two thousand years are forgotten from history.

- Description from Novelupdates

Riven was a young man with dreams as vast as the horizon, but life demanded sacrifice. To support his struggling family, he gave up his education and ambitions, shouldering endless work to keep them afloat. Yet, his loyalty was met with the ultimate betrayal by his own father.As his life slipped away, Riven awoke in an unfamiliar world brimming with magic, reincarnated by a mysterious system. Gifted with a peculiar mana heart that pulses with untold power, Riven is thrust into a realm of mages, monsters, and ancient secrets.Determined to rise above his tragic past, Riven vows to become the strongest mage in this new world, uncovering the mysteries of his strange mana heart and the enigmatic system that guides him.