What? I'm the Zombie Baby's Daddy?

A gamer who has crossed into a wasteland seven years after the zombie outbreak needs formula milk, a lot of it, and in that world formula has to be earned. The reason is a voice in his head calling itself the super dad system. On his first day there it made him take in an S-grade zombie infant, a girl, and told him that the ruins around them were a world full of love and peace. Before that he had been a shut-in who played games until dawn. He finds that a bottle and a pacifier will settle the child when she turns violent, so keeping her fed becomes his first job. He does whatever pays for formula, and between the work, which hardens his body, and the strength he can draw from the child herself, he gets stronger by the day, on the way to being the strongest father in the wasteland.