SPOILER WARNING
So as I remember, there's not much to hate about Renjaku's sister, I think. I'm not so sure because I couldn't read the raws well and I just pretty much skimmed through the chapters. But I did use a translator to some pages that really got me curious.
So anw, she will eventually get along with Hana and a very devoted and clingy aunt to Renjaku's and Hana's daughter, Tsubaki. (Yes you read that right. Hana will get pregnant and give birth)
As for Joel, the marriage partner candidate, I don't think there's much to worry about him. As to what I see and remember, he'll just pretty much shake up a little bit the relationship between Renjaku and Hana. And plus, he would somewhat develop a relationship with Aoba (Hana's brother). I also remember seeing the raws for the separate series for them. Aoba ended up being the uke
cont.
As for Hana's mother, well yes, she deserves all your hate for her. She tried to stop Hana on getting married with Renjaku, saying stuff like she will decide who Hana will marry. WTF. But of course she didn't succeed because Hana and Renjaku eventually got married. I remember also seeing Renjaku's mother attended the wedding.
That's all that I can recall. I'm really so excited to finish this series. I will also try to look for the sequel or spin off on Aoba and Joel's story. If they have officials too, I will try to upload it as well

Reading your comments and reactions makes me smile and laugh
I've read the raws to this like years back before it got an official release. So, if some of you want a little spoiler, comment below
Btw, if you guys are gonna ask for the raws, I don't know where to find them anymore because I've read that at the b@to site before