I felt the same about him. I think it's because I, personally, kinda went through a little of what he did. I was abusive to my partners. I won't give excuses for my behaviour because there really aren't any. I can say I had reasons for the way I acted and I had to get to the bottom of those before I could change my behaviour. With a lot of love, forgiveness and understanding from my husband, I was able to heal, grow and change. The person I am now seems so far away, and so very different, from who I was then. I can't imagine ever doing those things again. So, I really relate to Kan-chan. You have to WANT to change and move forward and it's not always easy to accomplish, but it is possible with enough courage to face the worst parts of yourself and with enough love and support from the people around you. I think that is the point the mangaka was trying to make with his story.
A few years back I read Yumi's and Kanchan's stories for the first time (Yumi's first) and I never hated kanchan. I always thought it was unfair the way everyone fucking hated his guts, wanted him to die, cut off his dick, the works. Idk idk I never hated him and idk why. He just seems so precious. Not saying anything he did was ok but I'm not holding it against him (personally). BUUUUUT IDK I just can't get behind hating him he's so cute (along with shuuna of course that flashy bastard)