Anime-Shippo, why did Mingka and Inuyasha go to collect the King of Four Souls?

Grandpa Meika is a flea demon and the father who followed InuYasha with Totosai. Later, after InuYasha's father died, he became a gravekeeper. Because of Sesshomaru's sneak attack, he was forced to leave the cemetery and follow Master InuYasha~ Shippo's father was killed by the Thunder Beast. In order to avenge his father, the little Shippo began to want to steal Kagome's Four Souls Jade. Later, Inuyasha killed the Thunder Beast and avenged Shippo. The helpless Shippo followed Inuyasha and his party. People are embarking on a journey to collect the Four Souls Jade! I am also a dog lover~