http://www.mangago.zone/read-manga/hadakeru_kaibutsu/
Here ya go. You should definitely read it, the ex got big character development. And felt guilty. Enjoy. :).
I'm not the one whom you recommended this sequel... but I was surprised by how much I liked it.
I didn't care for Ken-chan at all in this story. But in the sequel you get to feel his pain and regret for how he treated Yumi. And Yumi also admits that he was holding on the old Ken... it's very real and I loved how the author executed the story.
Thanks for recommending it!

i accidentally read the back story first , my gosh i cried a lot glad that he got out of the abusive relationship,,, i was genuinely scared the abusive ex wont let him go or smth