A brief description of the Ranker Who Lives A Second Time manga:
Yeon-woo lived for 5 years, resigning himself to the disappearance of his younger twin brother. One day he got his brother’s pocket watch. Inside, he found a hidden note. “Brother, if you are reading these notes now, I am no longer on Earth. Upon learning that his younger brother had gone to Obelisk. The Obelisk is a tower of gods that is somewhere in space at the crossroads of several dimensions. Yeon-woo decides to go there himself.