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Story

"Hey, don't get confused. I've never thought of you as my little brother. You don't even know your right place." That was the dagger that hurt the most. Myeong-U Han. A child of a wealthy family with a quick mind. But God didn't give him everything. A near incurable genetic heart disease. He did his best in order to earn the respect of the people around him. But his father, the chairman, and his family members never took him seriously. That was when an accident suddenly struck him. And... he woke up in the body of the severely injured student, Cheo-Min Kim.

Synopsis via AniList (English).