Complex sentence: Due to his original backstory having multiple plot holes, Hoshino rewrote it to one where Hoshino created Kanda's first friend, Alma Karma, who plays an impact in his backstory as well as alterations to Kanda's characterization.
Split into simpler sentences: Due to his original backstory having multiple plot holes, Hoshino rewrote it. In the official one, Hoshino created Kanda's first friend, Alma Karma, who plays an impact in his backstory as well as alterations to Kanda's characterization.