Yuudai Shimaki regularly unwinds at a local park between his university classes and part-time job on Wednesdays. During this time, a person wearing a dog costume hands out balloons to both the children and Shimaki. Despite initially wanting to turn down his offers, the person's disheartened expression makes Shimaki inclined to accept. Soon, Shimaki receives another balloon from the same person, but this time, he resolves to decline his advances. Hearing Shimaki's refusal, the dog-costumed man compels him to take it and timidly runs away. Shimaki is left alone, sitting on a bench and holding a balloon with a note written "I like you" on it. No matter the amount of balloons he gives, the person in the dog costume believes that these are not enough to properly express his heart—especially when these feelings have already formed long before their encounter at the park. [Written by MAL Rewrite]

Kigurumi-kun began as a web comic on the author's Twitter account on April 9, 2016. The series was published in book format with extras by Ichijinsha on February 15, 2018.