Complex sentence: Kō is described by several other characters, including Ichiyō and both Yūhei and Junpei Azuma, as very like Aoba, in particular with being as competitive as her, and Junpei attributes their frequent squabbling to their similarities.
Split into simpler sentences: Kō is described by several other characters, including Ichiyō, Yūhei Azuma, and Junpei Azuma, as very like Aoba. In particular, they say the two are both very competitive, and Junpei attributes their frequent squabbling to their similarities.