I believe it is a Chinese light novel
Main character is actually weak but studies a great deal. If he fails to get first place in an exam, he will die. But he hasn't told anyone this
He has a marriage certificate with the prettiest/most talented girl which he goes to return, only to be insulted.
After repeating above incident, he decides to keep the marriage certificate
He befriends the daughter of another ruler, gains the queen's favor, and his close friend is fairly powerful as well

A martial arts book where souls and internal strength are tied with bonding to a star

Ze Tian Ji

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Yes, that's it! Thank you very much