Complex sentence: He attempted to kill Kaoru when she hoped to learn more of her father through him, as she thought Kuramachi had met her father; she found out Kouhei actually never met Yuji Mitsuki, but was only inspired by his work.
Split into simpler sentences: He attempted to kill Kaoru when she hoped to learn more of her father through him, as she thought Kuramachi had met her father. However, she found out Kouhei actually never met Yuji Mitsuki and was only inspired by his work.