While her Mother is the spanner, but she makes them have a condition to be aware of their own situation. Honestly, they're both fragile. Their codependency, if not in sitcom, are actually either crashing or poisonously clicking.
"I want to be better for Hizumi because I know I'm worthless" vs "I want you to be worthless and NOT changing because I'll take care of you forever for a broken person like me,"
And even if he decided to live under Hizumi's care, his pride might not allow it. After all, that's his motivation to be better is to be with her.
Her mom herself admits she's terrible, but is also giving a strong question, "Do you want to be with her? (for your ego because you're worthless)" or "Do you want her to be happy? (Because obviously you'll drag her to your worthless life)".
What's worse, her Mom isn't hiding any dirty tricks. She's actually opening a stage for them both, to think and to talk from heart to heart. And that's what makes this scene actually painful. No misunderstanding. No hiding. Could they actually face their own flaw?