I really like this series. Despite its weaknesses, I found it an enjoyable shoujo supernatural romance, in part because there aren't too many love interests, and because of the way Chiko manages to blunder into all these family plots and secrets. The characters aren't unique but are endearing enough that you want to find out what happens to them.
The ghost-of-the-week arcs are decent enough, serving as tutorials on how to use the 5-coloured threads, but it becomes clearer that the focus of the series is really on the past. What happened several years ago to turn Akeo and Nadeshiko against each other (and to her legs?) ? What have all the s sacrificed to gain the powers they have gained? It's clear that the series will explain all of these as the past unfolds, and that Chiko herself has an important part to play in resolving all the intrigues and mystery surrounding the main family and their magical artefacts. I know it looks confusing now, but judging from the raws, rest assured that it will all eventually be explained.
I like Takeuchi's artwork, it may not be unique, but it still feels distinct enough to recognise. Too many shoujo artists have a bland style that isn't skilled enough or unique enough to make them memorable. As a shoujo artist, her characters are suitably pretty without being ridiculously stretched or disturbingly moody-looking, as a result they are appealing enough. She has improved since her previous series, the drawings of Nadeshiko in both make that particularly evident. I also like how Takeuchi really integrates the sound effects into her artwork. It must be hell for publishers and scanlators, but artistically it feels well-integrated.
I'm not actually a fan of age-gap romances or teacher-pupil ones (I know Akeo's not really her teacher, but still) but at least she's 17, so the idea of that romance insn't as disturbing as it first sounds. Whether this angle is a plus or a minus depends on readers' preferences. And given that this series is otherwise pretty tame in the romance department, it does manage to get by without being really squicky.
It's worth mentioning that the series features a couple of crossover characters from Takeuchi's earlier work, His Majesty's Dog, so if you liked Nadeshiko the refined but dangerously powerful disabled onmyouji/miko/family head, she appears in this series in a more major role than previously.
What the series really suffers from is actually not related to the series. It was licensed, but Go!Comi who were releasing it officially in English have long since shut down. As a result, we're unlikely to see any more official releases. Meanwhile, as you can see above, whilst the scanlators do a good job, the series has been scanlated at a particularly slow rate over the past few years I've been following it, averaging 2 chapters a year. They clearly need more help with this series (come on, guys!). It's this that makes it challenging to keep up with the series because by the time a chapter's come out, you've half-forgotten what happened recently and have to re-read it a bit.
In summary: Enjoyable supernatural romance with complex characters with their own problems, and an intriguing mystery behind their family curse. However, releases are infrequent, so although I recommend this series, you will be waiting for new chapters. If you read French, the entire thing has been released in that language, which might help.