Forgotten Title After being betrayed by his closest ally the Duke, King (or Emperor?) regresses to his childhood

Hello everyone, my first time posting on the forums here.

Trying to remember the name of this series. The main character had been killed in a war far in the future, after a betrayal from the duke he considered his ally. When he regresses to his childhood, he is a mistreated kid who gets picked up by knights loyal to the duke. I believe he's a slave? And has his necklace from his mother stolen by the guy in charge of slaves, or something similar. When returning to the Duke's estate, he is given ridiculous looking clothes, and asked to enter from the back gate instead of the front gate of the estate. The point being to ridicule him, and also undermine his authority as a prince. Within the estate, he is also relegated to the abandoned portion of the estate, and he has to ask his knights to clean it up for him. Apart from those details, I remember he also was taught the royal swordsmanship said to be only for ceremonial use, but is actually able to use it surprisingly well.

I've been trying to find this series again, but have been having a surprisingly hard time. The website also used the same layout as what genesis translations site does I believe. Any help would be appreciated.

 

This Bastard is Too Competent

 

THANK YOU. Really appreciate it!