Complex sentence: Karyuudo manipulates his own daughter, Hinata, by giving her his diary to attack Aru Akise, believing that he knew that Karyuudo was responsible for the recent savage murders and that Akise was a Diary Holder, though he was mistaken on the latter.
Split into simpler sentences: Karyuudo manipulates his own daughter, Hinata, by telling her to attack Aru Akise, believing that Akise knew that Karyuudo was responsible for the recent savage murders. Also, that Akise was a Diary Holder, though he was mistaken on the latter.