Yokohama Kaidashi Kikou

From Seven Seas:
In a future Japan, long after an environmental catastrophe, Alpha the android runs a small café in a seaside town. As she wonders if her absent owner will ever return, she stands witness to the twilight of humanity with coffee, a slice of watermelon, and the sound of her moon guitar. Alpha and her fellow residents enjoy the melancholy beauty of life, even as the end approaches.

Note: Won the 2007 Seiun Award for Best Manga.