Friend or Foe?

So, this is a prequel from my last fanfic. Izaya made a promise to his sister that he will make it up to Yumichika. Yumichika still refuses to talk to him as Gin had to intervene in between them. Yumichika passed out as he is now in squad four getting treated. Will Yumichika & Izaya will become friends again? Or be enemies forever?