In his lifetime, Tsukiguni Yoriichi had only one encounter with Kibutsuji Muzan.
At that time, the Demon Slayer Squad had just recently introduced the breathing techniques pioneered by Tsukiguni Yoriichi, which had indeed narrowed the power gap between humans and demons. Yet Kibutsuji Muzan still believed that the mere human Demon Slayer Squad posed no threat to a powerful demon with extraordinary abilities. Thus, he did not actively seek to eliminate the squad.
Especially after clandestinely observing the performance of the most outstanding swordsmen of the Demon Slayer Squad, Kibutsuji Muzan was even more convinced that he, as a perfect creature, could not be defeated. Although he was initially interested in the breathing techniques, his interest quickly faded.
That was until the day Kibutsuji Muzan encountered Tsukiguni Yoriichi.
