Yoriichi was born with a unique ability to see and manipulate sunlight, which he used to fight demons. He also possessed exceptional physical strength and agility, as well as incredible swordsmanship skills.
Yoriichi was instrumental in developing the techniques that the Demon Slayers used to fight demons. He was also the one who created the Breath of the Sun technique, which is considered to be the strongest and most difficult of all the breathing techniques.
Yoriichi's backstory is tragic - he lost his family to a demon attack when he was young, which fueled his intense hatred for demons. Despite this, he remained a kind and gentle person, and was greatly respected by his fellow Demon Slayers.
In the series, Yoriichi's legacy is carried on by his younger brother, Michikatsu Tsugikuni, who also becomes a Demon Slayer and adopts the Breath of the Sun technique.