Ability: Can distinctly judge anything to be Good or Evil
One of the gods that resides in hell and judges the deceased. Her ability allows her to get things settled once and for all. Her actual name is Shiki Eiki, and Yamaxanadu part is a kind of title for position in Yamas. Basically the title represents the place they're in charge of.
Unlike humans, she has a criteria of right and wrong in her own mind. Her judgement cannot be overturned by the deceased. Her criteria is quite complicated, and the seriousness of the crimes factor in everything from why they occurred to the personal history of those involved.
The minimum requirement of lying to her, in order to appear as a good person, is not letting her discover that lie. If discovered it is a huge deduction.
Her usual routine is to find faults of the deceased and decide where they will be sent to: Hell, Heaven, or somewhere else. Due to her job, she tends to be somewhat moralistic.
It was when Komachi did not ferry the deceased to her that she noticed something was wrong in Gensokyo. Suspicious, she looked at Gensokyo only to find out that it was blanketed by flowers.
All kind of flowers were blooming at the same time - spider lilies, sunflowers, lilies of the valley, lotus blossoms, and cherry blossoms. As she was digesting this, both living humans and youkai attacked her, seething with anger.
These assaults immediately made her realize what was going on.
Now it is "that year", 60 years since the previous one.
All these flowers were possessed by spirits of the deceased, and the reason they weren't processed properly was because Komachi was being lazy.
Komachi, being too easygoing, only thought "ah, it's beautiful" even when the flowers were filling the whole place.
It's not like she can restore the flower-covered Gensokyo, but time will eventually bring it back to normal. There was little to no harm.
However, a human who's been charged with a crime is before her. With her pride, she couldn't let her pass through her place.