Shiba Mirabu

Shiba Mirabu was one of the finest students ever to emerge from the Dai-Chikai Dojo. His toughness and knowledge meant he would be just as capable of debate as battle. This coupled with his great sense of loyalty was a sign of great things, but when the time came for him to take a charge, Shiba Tsukune came to him and asked him to guard her son Shiba Aikune. His decision to remain faithful to Aikune put him at odds with both the Elemental Masters and his sensei Shiba Saisune. (Samurai p. 58)

A Demon's Prophecy
The Onisu Hakai once told Mirabu that Aikune would kill him, and he would be remembered as a traitor, yet it still does not deter his loyalty to Aikune. 

Phoenix Clan Champion
Mirabu was made Champion by the Elemental Masters shortly after Shiba Aikune's disappearance. Recently, due to Aikune's mastery of Isawa's Last Wish, the lost Soul of Shiba has been magically bonded to the Shiba bloodline and the Ancestral Sword Ofushikai has been returned. Mirabu is the first to hear the soul of his ancestors since Tsukune's Acsension, and proves him as the rightful Champion.

Isawa's Last Wish
After Shiba Aikune died in 1168,Mirabu became the bearer of Isawa's Last Wish.