The funny thing about the Romance of the Three Kingdoms is that Cao Cao was never actually an emperor

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While he was posthumously honored as an emperor of the Wei Dynasty later on,
his official title while in office was "King of Wei."
It was only after his son, Cao Pi, deposed Emperor Xian that Cao Pi ascended as emperor (Emperor Wen of Wei).
What's even funnier is that Liu Bei also became the emperor of Shu Han, but died only about a year later.
Afterward, his foolish son Liu Shan reigned as the emperor of Shu Han for 50 years.
The same goes for Sima Yi.
They say Sima Yi unified everything,
but while he was in office, Sima Yi never even became a king.
His son, Sima Zhao, became king,
and then his grandson, Sima Yan, deposed the Wei Emperor Cao Huan to become emperor himself.