Kimi to Boku no Uta World's End(2004)

Kimi to Boku no Uta World's End

In a world where everything was lost, our paths crossed. An unidentified epidemic exterminated humans in half a year. Hazufumi, a teenager who miraculously survived, lived lonely in this desolate world. He rejected to attain important things because he knew the pain when losing them... He happened to cross by a girl. A weird girl being followed by a hundred cats.And meeting with her changed Hazufumi's heart. (Source: Baka-Tsuki)