High school student Yu Yang, because of coming in last on his history exam, accidentally awakens a book spirit from a blank ancient book left behind by his grandfather, gaining a chance to time travel. He travels to Zhuozhou at the end of the Eastern Han Dynasty, turning into Liu Bei, and takes the Oath of the Peach Garden with Guan Yu and Zhang Fei. The book spirit tells him he needs to live until the Three Kingdoms are divided in order to go home, but does not guarantee the life and death of Guan Yu and Zhang Fei. Amidst the troubled times, using his modern common sense and a "fear of death" mentality, Yu Yang is mistaken by Guan Yu and Zhang Fei for being farsighted, benevolent, and generous. In battles, he always hides in the rear or pretends to command while actually being extremely terrified, yet unexpectedly earns the reputation of "Benevolent Elder Brother" due to the bravery of Guan Yu and Zhang Fei.