Yin-Yang Harmony System - Chapter 13

Stranded in a world not his own, in a body not his own, Kaden finds himself stuck as a low rank marine in treacherous waters in the middle of an ocean where only the strongest can survive and a count down until a war that would shake the oceans and the very world itself erupts, where the kings of the sea will devour the chum. Gamer System. Insert.

[Nakseong High School, the heads of 300 people exploded!] Lee Joon, an ordinary high school student.During the entrance ceremony, he was caught up in a strange phenomenon and died.[You have died.] [Restarting from checkpoint.] [Loading…] And then a message appeared before his eyes.『Welcome to Nakseong High School that is full of mysteries and secrets.Uncover the dark secrets hidden around the school, or fight against urban legends and myths to earn points and unlock special abilities.Then, gather companions and stop the resurrection of the demon king before you graduate.The world is in your hands.』

Ethan finds himself mysteriously transported to another world, where the strong reign and the weak perish.Welcomed by a kind farmer who decides to help him upon seeing his poor condition, Ethan begins to hope for a new life.However, his dream is shattered when an acquaintance deceives him, leading to his sale at the slave market. Desperate and confused, Ethan wonders what he has done to deserve all this.“Which deity have I offended to deserve all this?”Just when he thinks all is lost, fate has another surprise in store for him, once again changing the course of his destiny.

…but it seems pretty doable.