https://series.naver.com/novel/detail.series?productNo=2500884
Infinite Leveling Murim is a series authorised Gonbung and illustrated as a manhuwa by Jinwoo Kim, which is published weekly on Naver.
https://www.webtoons.com/en/action/infinite-leveling-murim/list?title_no=2676
In the ancient land of Murim, it is the end of the Era. Cheonma the Heavenly Demon appeared from nowhere and unleashed chaos upon the Murim Alliance, sweeping away all those who opposed him with his overwhelming might. Weakened from within by internal corruption and masters only out for their own self-benefit, in the face of this overwhelming foe the alliance can do nothing but crumble.
In the final days of the alliance's fall, Yuseong Dan is a lowly captain overseeing a squad of foot soldiers at the Alliance's final stronghold. Ordered into a futile attack on the unstoppable Cheonma to cover his cowardly superior's retreat, Yuseong ends up the final solider of the alliance to fall at Cheonma's hands. Despairing over his lifetime of failure to achieve anything he wished for, Yuseong's last thoughts are spent bemoaning his father's advice that a lifetime of effort will surely reward him...
...before he wakes up as a young child on the day of his entrance examination for the martial arts military academy, somehow having been sent back 30 years to his youth. Even more perplexing to Yuseong is the mysterious floating tiles appearing around that only he can perceive, giving him 'missions' to complete for the promise of rewards. Though greatly confused, Yuseong soon discovers that by completing these missions, he is rewarded with greater strength, endurance and speed, along with techniques and skills beyond what he could ever preform as a lowly grunt in the alliance. Armed with his knowledge of the bad future to come, Yuseong resolves himself to 'level up' through this mysterious phenomenon to become the world's best warrior and avert the catastrophe that is Cheonma, in the process also protecting those who met an unjust end along the way and becoming a hero that the Alliance needed to save it from itself.