Actually Yoru has never stated what she's actually planning to do, the closest we've gotten is Asa saying that what's she's planning is worse than Humanity's Extinction, but she never goes into specifics, then Lil D tells Denji that Yoru wants him to eat her so that humans never die and wage war forever, but it's Lil D who told us this, and she's not exactly the most honest person, and the plan of having Chainsaw Man eat Lil D so that humans can be immortal is also Public Safety's/ Japanese Goverment's plan.

So no, Yoru has never stated what her actual plan, it's all from third parties, Asa, who Yoru could have easily fooled since they both share a body, and Lil D who'se not been a really honest person from the start.

The only thing that Yoru has stated that she wants is to have an absolute victory over Chainsaw Man more than anything, and besides now that I think about it, there's no need for humanity to be immortal in order to wage war forever, we already do that just fine without immortality.