yes. the king sent them
King: "Ah yes, my childhood friends' sister was finally found safe and sound after going missing, though with apparent amnesia, which caused her brothers to slip farther into insanity.......................... I want to date her."
forget date..dude wants to marry her like wth. and you know he had to go out of his way for this bc the entry period is already over and he personally sent those letters. And he sent 23 LETTERS incase her brother ripped it up. what an......interesting guy
Honestly it sounds more like him just wanting to tick his friend off, while also being curious about her (though with the two being childhood friends, they never said so far how the king and the sister interacted bc the MC reincarneted into her body
* ¯_(ツ)_/¯
So wait, the letters are from the palace?