Heavenly delusion is a great adventure mystery that puts an emphasis on immersion and let's the viewer figure out the mystery as they continue watching. With all that, it manages to add comedic and immersive elements that engage the viewer in the story further. If you're looking for a mystery, psychological thriller and/or adventure in a different world than our own, this is the anime for you.
I want to give additional praise to this story for being able to address some difficult and touchy subject in a mature and respectful way. This story includes characters who are children and teenagers, and experience the difficulties of growing up in different environments. It flawlessly combines the mystery aspects with the problems the characters face, while including subjects such as sexuality and puberty, illness and identity in a way that feels realistic and not explicit. There is no focus on the private or physical aspects of uncomfortable events, and the imagery is not inappropriate or disturbing when there is no need. In other words, this story doesn't need to rely on sheer shock value to engage the viewer, and it's aware of this fact.
Please consider that this is not the full story of the manga, and obviously does not aim to fully conclude the larger storyline. Though it does lose and conclude several shorter storylines which are very engaging.
Besides, it's a very short watch, and a very high quality one at that.