Touhou Sangetsusei: Eastern and Little Nature Deity is a rather short manga. The background arts are not that special. The characters do look better than in the games, but the art isn't all that great either. However this show does complete its role in expanding on the lore. Rather than explaining an origin story; Through dialogue and character interaction it explains specifics. The information present isn't necessary to understanding the world. In fact, the information might seem useless, but it still serves a purpose. It is extra world building, nothing dramatic.
The center of this world building
lies the powers of the fairies. The magic system and everything is really softly described. The existence is only stated. People who enjoy "hard magic" and like concrete stories will probably not have a good time with it.
The merits of this manga lie in the culture of this story. The fairies, the references to Japanese lore such as Bakenekos, puns, and the way these are integrated to the world of Touhou.
It isn't quite funny but as an exploration of culture and humor that involves references to that culture it can be quite fascinating. I spent more time searching topics up than reading this manga.