Chibikoro Tenseisha no Mofumofu Morigurashi

Souta wakes up in an unfamiliar forest. And next to him, a talking bird and a giant cat fast asleep; wait, had he shrunk? Guided by voices calling for help, Souta is reincarnated into this world as a three-year-old child. When he awakens Haku, the giant cat who rules the forest and has been causing the drought, all sorts of creatures take notice! Thus begins Souta’s life in the otherworldly forest, navigating his tiny body while living alongside fluffy, magical beasts!

(Source: Micro Magazine-sha, translated)