Hiro and Zero Two die in the process of defending Earth from VIRM, and the series ends with the two of them meeting again as children, having been reincarnated on Earth, where the human race is now thriving again.

What happened to Hiro and Zero Two at the end?

Hiro and Zero Two die in the process of defending Earth from VIRM, and the series ends with the two of them meeting again as children, having been reincarnated on Earth, where the human race is now thriving again.

Why did Hiro and Zero Two have to die?

In the anime, Hiro and Zero Two sacrifice themselves to destroy the VIRM planet and save the future of their friends and planet, and they are reincarnated into human children 1,000 years later. Whereas in the manga, they survived the final battle and swore to be together forever.