Mandarin Orange Picture diary

An elementary school student, Tomu Kusanagi, picks up an orange male cat with a mysterious atmosphere, names him "Mikan" and decides to keep him at home. One night, he witnesses Mikan talking to herself in human language while drinking in the kitchen. Mikan is a peculiar cat who has come to be able to speak human language while living with "Grandpa" who used to have Mikan. In addition, Mikan can stand and walk on two legs, and can even write and draw with great dexterity. Tomu and her parents accept Mikan's secret and decide to live together. (google translated)