Choi Woori has spent the last three years living alone, and the only remedy to her loneliness is the company of her five-year-old poodle mix, Maru. But one morning, something miraculous happens: standing on her bed is a five-year-old girl calling her "big sister"—Maru has turned into a human child!

Woori barely has time to adjust to the whole situation, as Maru has kept some of her puppy-like habits. She still tries to bark, she grabs stuff with her teeth, and their daily walks are slightly more challenging without a leash. With her boundless energy and irresistible charm, Maru often attracts the attention of their somewhat eccentric neighbors, promising that loneliness in Woori's life is now a thing of the past.

Maru Is a Puppy is originally a webtoon series which was published in print by Moon Phase (문페이스) from July 20, 2023, to October 5, 2026. The series has been published digitally in English by Webtoon Entertainment since September 2, 2023.