Tomcats (2005)

Blurb:
Pint-sized Human Cats, Shady “Men in Black,” A Cat God and More! Mao is just your typical disillusioned young man working in a pizza joint. But he soon finds himself in the middle of a surreal adventure after he meets his old friend Sora, a pint-sized human cat. Shady “men in black” show up at his workplace, prompting Mao to flee the city for a forest in the middle of the desert. Mao’s back-to-nature escape wouldn’t be complete without his silent lover Tora, Koyuki the magic human kitten, who can make all sorts of things appear, and more pint-sized human cats. Out of a door in a tree emerges a confused cat god, but even stranger still is what’s inside the tree! Yaoi in Wonderland?!

Source: www.anisearch.com/manga/1679