Miyatsuka Mahoro has always been able to see and communicate with spirits, known as ayakashi. After her grandmother's death, she takes over the caretaking duties of a house filled with those spirits. The chapters of Ayakashi Ko are largely stand-alone, loosely tied together by the cast, and occasionally, past events. It's a fluffy slice-of-life story filled with likable characters and heartwarming tales. The art is rather simplistic, never going into too much detail either in the characters themselves, or the backgrounds. But this isn't necessarily a bad thing. Each character is unique in design and easy to tell apart, making a large amount of details unnecessary. Thisstyle gives everything a lighthearted atmosphere that's perfectly suited to the stories being told.

The characters are almost exclusively female, both ayakashi and human. Our human cast is comprised of Mahoro, the granddaughter of the original caretaker of the house, and later on, a German/Japanese transfer student named Takanashi Emi. Her goal is to befriend as many ayakashi as she can, though this is made difficult by the fact that she can only vaguely see them. With Mahoro's help, she not only gains the ability to see them clearly, but also has the opportunity to meet many different ayakashi.

The ayakashi - and the tenants of the house - are Kii, a tiny zashikiwarashi (house spirit) whose favorite thing is food; Kuuko, a kitsune spirit who loves mischief and can create illusions; Yukime, a gentle yukionna who has a fondess for sleeping in the refrigerator; and Nene, a newly-born nekomata ayakashi who is still learning what it means to be a spirit.

All in all, the plot of Ayakashi Ko isn't very deep, but it easily achieves what it's meant to be - a light story about the day to day life of ayakashi and the humans who care for them.