Give to the Heart: Memories (2015)

Blurb
On the colonized world of Mars, Dr. Ano, her assistant Chio, and their friend Ganok existed as gods, joined as one in a technological union with the supercomputer Margot. They formed a trio of immortal Demon Kings who determined the fate of all life on that planet. But long ago, they lived as normal humans on Earth. They went to school together and bonded through shared hardships. They even experienced love. All the while, the powers-that-be kept a nervous eye on Ano’s dangerous research. If left unchecked, her research could destroy human civilization. This is their story.

Source: www.anisearch.com/manga/27200