I read a manga a while back. From what I remember the main character always wears the same clothes (picture below, excuse the bad quality since I drew it myself). There was a joke that lasted a page or so that when the protagonist opened his wardrobe/closet, there were a lot of pairs of the same clothes. Pretty sure it was a sleeveless shirt/jacket, although it might not be sleeveless, it was definitely black.
The main character is or was a general, can't quite remember. He had a either a demon sword or a very infamous one. The protagonist had a castle and a small army. He also met this princess when he wasn't very well known yet (the princess was a lot younger than when the main story takes place). They don't recognise each other until they traveled together quite a bit. I most likely read it on isekaiscan.com (the manga wasn't an isekai), since that's the only site I used when I read it. I remember finding it on kissmanga accidentally as well, but it was still quite a while ago. Also, it was a japanese monochrome comic just to be specific.
To describe characters in a few sentences, and in a bit more detail:
The protagonist - He was a general that got pretty infamous due to how many wars he won. He met a princess while he was still a general, and then later met her when he became a mercenary (or a noble/lord, can't exactly remember). He owned a castle/fortress and a small army. After meeting the princess they traveled together for a while before recognising eachother. He had black hair and, if I remember correctly, he also had black eyes. He also had a well known sword, because it was a demon sword (might not specifically be a demon sword, but one that sucks someone's life/decreases the wielder's lifespan).
The princess - Can't remember much about her except that she liked the protagonist and also had bright hair (can't tell exactly, since it's in black and white).