Unless they had seen him in battle, or the more unlikely option of him opening up to someone, no one truly knew Yoriichi, he had been the only one to ever cut down that man, and although Muzan certainly ranked high on his list of enemies, there existed one person, one man, which Yoriichi truly regretted.And it was up to him, to cut down his own brother, until he did that, his soul couldn't rest. Hoping for some beta reading so feel free to drop some constructive critisism

op Rimuru goes to soul land for fun