Big Hero 6 (2014)

Blurb:
When Hiro's kindhearted brother, Tadashi, vanishes through a portal to save him, the boy genius is devastated. But his big brother left something to help Hiro cope with his loss ‒ a personal health-care robot named Baymax. And when what Hiro needs more than comfort is an explanation of his brother’s disappearance, Baymax ‒ with a few upgrades ‒ may be just what the doctor ordered! With new friends and Baymax 2.0 by his side, Hiro is determined to get to the bottom of everything... and he might end up saving the world on his way!

Source: www.anisearch.com/manga/16482