how did muichiro die

Muichiro Tokito died during the battle against Upper Moon One, Kokushibo, who is also revealed to be his ancestor. In the fight, Muichiro managed to embed his Nichirin blade into Kokushibo's body but suffered a fatal injury himself — his lower half was cut clean off by Kokushibo's chaotic slashes, guaranteeing his death. Despite his young age of 14, Muichiro showed formidable skill with mist-based techniques but ultimately did not survive this encounter.