Jinrui wo Metsubou sasete wa Ikemasen

On his way home from work, 26-year-old salaryman Osamu Kawakita encounters an alien named Lilin. She and her species plan on invading the earth, but she ends up getting stranded on this planet. Can Osamu raise her to become a kind-hearted kid before her species eradicates humanity in five years?

(Source: MangaDex)