There's a completed two-volume SF manga called "Kinu-Roku." It wasn't axed; apparently, it was planned as a short series from the start, but it was interesting enough that ending it in just two volumes felt like a waste.
It's set in a distant cyberpunk future.
Once upon a time, people tried to emigrate to Mars. Utilizing their own advanced science, they modified their bodies to survive Mars' harsh environment and successfully evolved into a new human race known as "Martians."
Earthlings, eyeing the Martians' scientific prowess, declared war on Mars. However, the war fell into a stalemate, and a long time has passed since then.
The protagonist, "Roku," is an ordinary instant-noodle vendor on Earth who lost his body in an accident, became a cyborg, and works steadily to pay off his cyborgization debts.
The heroine, "Kinu," is a "Mars-born girl" created by British intelligence after numerous failures by mimicking Martian technology. Intelligence had planned to mass-produce Martians from Kinu, the successful prototype, to use as weapons.
However, Kinu escapes from the agency, takes Roku—whom she happens to meet—hostage at gunpoint, and drags him along on a desperate flight toward Mars, where her own kind live.
Intelligence squads and failed Martian prototypes who are Kinu's older sisters and brothers attack one after another as pursuers.
At first, Roku was dragged along against his will, but as they survive life-or-death situations together, a friendship blossoms between him and Kinu.
Along the way, Kinu and Roku encounter a group of mechanical monsters called the "Fifth Wintering Party."
The Fifth Wintering Party is a remnant faction of Russians—a group of crazy scientists who replaced their entire bodies with machinery.
Earth has experienced four ice ages in the past, and they call themselves the "Fifth Wintering Party" based on the ideology that "we are the ones who will survive the coming fifth ice age and become the rulers of Earth."
From the perspective of the Fifth Wintering Party, the existence of Martians is "an abomination trapped by the shackles of the flesh," and they attack Kinu with open hostility.
Continuing their flight while targeted by both intelligence and the Fifth Wintering Party, Kinu and Roku manage to acquire a rocket bound for Mars, aided by an underground pro-Martian organization.
Kinu invites Roku, saying, "I like you, so why don't you come to Mars with me?"
Roku hesitates a little, but chooses to stay on Earth, saying, "There are still things I want to do here."
Kinu's rocket enters launch preparation, but it gets surrounded by intelligence.
Furthermore, the Fifth Wintering Party arrives as well, leaving them surrounded on all sides—a hopeless, life-or-death crisis.
Just when you'd expect the worst, the Fifth Wintering Party attacks intelligence and lets Kinu escape.
"Go! Daughter of Mars! You are a messenger! When you reach Mars, tell them this! We, the Fifth Wintering Party, will eventually seize even the sun and rule over everything!"
When Roku returns to his instant noodle shop after seeing Kinu off as she escapes Earth, his estranged mother—who had abandoned him and eloped—has returned with a young daughter (named Seven, I think) she made with some man.
500 years later.
Martians observe that the light of the sun is beginning to wane.
It seems the Fifth Wintering Party truly conquered Earth after the fifth ice age arrived, surrounding the sun with a gigantic Dyson sphere and seizing even the sun, just as they declared.
A high-ranking Martian hints at war, saying, "A clash between the Fifth Wintering Party and us Martians is inevitable."
Kinu, now 500 years old and taking the form of an adult woman, states, "I desire dialogue with them, not war," while thinking of Roku in her heart.
The final panel shows Roku living peacefully with his mother and younger sister.
It leaves a lingering sense of unease not knowing what happened to Earth 500 years later. Well, Roku himself was human despite being a cyborg, so he wouldn't live for 500 years anyway, but still, seeing Kinu—driven by her memories of Roku—not wanting a war with Earth felt so heartbreaking.