When the protagonist traveled through time, it happened to be the eve of Li Chengqian's rebellion or the time when Li Tai's heir apparent was at its peak. The original owner may end up miserable because he took the wrong side or was accidentally involved.
With his knowledge of history, the protagonist knows the strengths, weaknesses, and endings of each brother. He used his identity as a "child" to "talk like a child" in front of Li Shimin, complaining about the extremeness of his eldest brother, the hypocrisy of his second brother, and the cowardice of his third brother (Li Zhi).
His complaints were precise and sharp, often hitting the nail on the head. When Li Shimin was troubled, he felt that his younger son was seeing things more clearly.
