Ninth Life Love

From the Digital Manga edition

Six years ago, Koharu lost his beloved cat, Dorasuke. There is not a single day that goes by that he doesn't think of his cat. Then, out of the blue, he meets a guy...and it turns out that it's Dorasuke! God gave him a second chance to be with Koharu - and this time as a human! But there's a catch - God made him a promise that he must keep, and if he breaks it, there'll be consequences...

Source: Anime News Network Encyclopedia