See, he's already won a (minor) stupid prize for keeping quiet about her involvement. Hanabi is definitely gonna try to strike back at him for this, I don't think a manipulative narcissist like her will just quietly fade away after being told she's hated. I don't believe for a moment this is the last we'll see of her.
I'm still annoyed at how he refused to just start dating Fumi and that he still has to do this "trial period". Hanabi will likely continue to harass him regardless of whether he dates someone or not. And she's probably going to find out his relationship with Fumi anyway.