Read Manga Uchuu Kyoudai online in English. Also known as Space Brothers, Uchu Kyodai, and 宇宙兄弟.

As children, Mutta and Hibito Nanba made a reckless, awe-struck promise beneath a star-strewn sky: the older brother would set foot on Mars, the younger would walk the moon. Years later, that vow has split into two wildly different realities. Hibito, the charismatic younger sibling, is on the verge of becoming the first Japanese astronaut to land on the lunar surface. Mutta, meanwhile, has just been fired from a comfortable auto design position and finds himself adrift at thirty-two, headbutting car doors in frustration, genuinely uncertain where his life derailed.

Then a letter arrives from JAXA. Against staggering odds, Mutta has been selected to enter the country's grueling astronaut candidate program—a second chance that feels like the universe itself is daring him to remember who he used to be. What follows is not a simple underdog story. The examination rooms, isolation tests, and press interviews peel away ego and self-pity, forcing Mutta to rely on a peculiar blend of stubborn optimism and the quiet wisdom gained from failure. The series entrenches itself in the psychological unmaking and remaking of a person long after a bygone promise is made. Mutta and Hibito drift apart and collide again, their bond stitched across the distance between Houston, Tsukuba, and the silent depths that wait beyond Earth's atmosphere.

This series may appeal to readers who enjoy grounded science fiction, character-driven adult drama, and stories that treat a second shot at a childhood dream with uncommon sincerity and humor.