Hated Madoi on the rape part, who would like that? Ofc that's scary af.
I have great interest on DID or split personality disorder so I enjoyed it... AGAIN NOT THE RAPE PART!
I think, Madoi might believe that the best way to protect Kou is to dominate or control others who pose a threat, even if this means resorting to violence or abuse. Kakeru punched him and that might've trigger Madoi to come out.
In some cases, alters might reenact aspects of the trauma they experienced. This can sometimes result in behaviors that seem abusive or aggressive, as they are re-living or expressing unresolved trauma.
Kou was sexually abused by his mother (I might be wrong
Tracing His Silhouette