Shounen

Second Life Ranker summary:

Yeon-woo had a twin brother who disappeared five years ago. One day, a pocket watch left by his brother returned to his possession. Inside, he found a hidden diary in which was recorded “By the time you hear this, I guess I will be already dead….”
Obelisk, the Tower of the Sun G.o.d, a world where several universes and dimensions intersect. In this world, his brother had fallen victim to betrayal while climbing up the tower. After learning the truth, Yeon-woo decided to climb the tower along with his brother’s diary.
“From now on, I am Jeong-woo Cha.”

Tales of Demons And Gods summary:

Killed by a Sage Emperor and reborn as his 13 year old self, Nie Li was given a second chance at life. A second chance to change everything and save his loved ones and his beloved city. He shall once again battle with the Sage Emperor to avenge his death and those of his beloved . With the vast knowledge of hundred years of life he acc.u.mulated in his previous life, wielding the strongest demon spirits, he shall reach the pinnacle of Martial Arts.
Enmities of the past will be settled in this new lifetime. “Since I’m back, then in this lifetime, I shall become the King of the G.o.ds that dominate everything. Let everything else tremble beneath my feet!”