With Chainsaw Man's recent developments, the spotlight seems to be on the new transfer student. At this point, nearly everything points to her being the Death Devil, especially when her "special powers" were teased in chapter 196. Considering that she is Lady Death after all, then she arrived earlier than expected and could begin her work soon.
However, what's also being carefully looked into is Yoru's plan. Following Asa Mitaka's recent resurfacing, the War Devil within her seems to be planning something unspeakably terrible. Going off of recent theories, the speculation is that she aims to defeat her sister to create a world without Death. Indeed, a world without Death or the fear of it could be ideal for Yoru.
Disclaimer: This article is purely speculative in nature and reflects the writer's opinion.
Chainsaw Man: A Deathless world would be ideal for Yoru

Chainsaw Man's War Devil stands as a uniquely cunning and difficult-to-read character. Her impulsive and erratic approach throws readers off when it comes to figuring her out, but then again, it is obvious that she too has ulterior motives in this chaotic Devil-infested world. Now given the manga's recent events and speculations, if Yoru's plan bears fruit, a Deathless would be ideal for her.
Assuming that either Chainsaw Man or her wielding Chainsaw Man (after turning him into a weapon) defeats Death, she will likely have him erase her sister. As per series lore, whenever Pochita consumes a Devil, the concept as a whole ceases to exist. This means that Death itself becomes void and hence immortality is added to the equation. Now with Death gone, Humanity and Devils cannot die.
In essence, this would create a chaotic world with constant war and strife, as Devils do not need to fear reincarnation upon getting killed, as they simply wouldn't die. At the other end, Humanity would face endless torment, making them fear the ongoing conflict, which in turn would power Yoru to a massive degree. Thus, she could then probably become what stands at the top of the food chain.
Would such a world really be ideal for Yoru?

The idea of a world devoid of Death in Chainsaw Man does sound intriguing. Not to mention, it would definitely be a lot more chaotic and messy than it is now. Also, undoubtedly Yoru would receive a massive power boost as humanity would grow to fear the constant war, destruction, and torment that burns the world around them endlessly.
However, it wouldn't be incorrect to say that after a certain time, they would grow accustomed to it. To elaborate, like the Devils, since humans cannot die, they would develop a sense of courage and rebellion. The realization that they cannot meet their end could dimish, and in some cases totally wipe out, the fear that they initially felt from the chaos.
So with this, they would grow more confident (in a sense). This again could lead to a spillover effect on Yoru, dimishing her newfound strength as lesser people fear War. Thus instead of cower in fear, they might start fighting back again. However, this thought process has its flaws too - for instance, pain still exists and things that mean to kill won't, so victims would experience endless pain unless rescued.
Final thoughts

In conclusion, while a world without Death might seem ideal for Yoru, the long-term consequences could harm rather than benefit her. Initially, she would thrive in a state of perpetual war, feeding off of and growing stronger through humanity’s fear and suffering.
However, as people understand their immortality, their fear might diminish thus weakening her influence. In addition, while Death would cease to exist, pain and suffering won't, leading to endless torment over true dominance.
Such a paradox poses questions around whether or not Yoru's ultimate goal would actually benefit her in the long run. Chainsaw Man’s world flourishes on incalculable chaos, and a scenario like this further layers the ongoing conflict between Devils and Humanity.
All in all, Yoru's ambition puts forth an interesting possibility, but its implications remain complex and open to question, thereby reiterating the series' unpredictable nature.
Related links:
- Devils' hatred for humanity may not be their fault in Chainsaw Man
- Nostradamus' real-life prophecy may foreshadow Yoru's plans in Chainsaw Man
- Chainsaw Man's Four Horsemen Devils' personalities all but confirm Death Devil's debut in chapter 195