Otouto no Omokage

It's the 10th year of the Taishou era. At a health exhibition, a mysterious friendship blooms between Akihiko, a boy who dreams of becoming a military doctor, and Hisao, who has a metal prosthetic arm. But each time Akihiko meets him, Hisao continues to waste away, and his prosthetic limbs proliferate... A retro Sci-Fi drama overflowing with darkness and beauty that questions humanity and its agency! (Source: Kodansha)