I think this is more of an explanatory info rather than a review, but let me write it for others to learn about this because there's just no way of watching a complete version of this anywhere online.
To directly quote MegaFrog, a small YouTube channel who made a video titled "Touhou Iceberg: Explained" at 23:32 of the video :
"In 2010 studio UFOtable announced that they would be working on an OVA to celebrate the 10th anniversary of the anime character Goods Store.
The OVA would feature a crossover between anime's mascot "Anime Tenchou" and the Touhou Project.
A trailer was released and the studio confirmed that the
final product would be released at Anime "Ichigo Shiba Shoujo Matsuri" event (I most likely heard it wrong) on November 20 of the same year.
Despite being credited in the trailer, ZUN confirmed on twitter that he had no involvement with the project.
As promised, the OVA was shown at a private screening on November 20th. Though no footage of this screening has surfaced online.
At the end of december the same year, UFOtable announced that a DVD of this OVA would be sold in stores. Though there is no evidence that this DVD was ever released, and no digital rips of the OVA have surfaced online. This may have been due to ZUN's strict policy on commercial Touhou content causing legality issues.
Credit to this video by Anime Top Scholar for compiling this information"
So, really. I don't know how this anime got onto MAL in the first place. But when I was still new to Touhou, like many others, and those who use MyAnimeList, will be confused that this anime is here in the database first place.
Regarding the anime and my own opinion on this, I don't remember much and I have no idea how I even managed to watch even a small part of this anime because I can't find it anywhere currently.
I probably watched this on a piracy website back in 03/18/2017 as cataloged on my On-Hold list.
All I can say is that the audio, animation, art, music, are great. It's by UFOtable after all.
As for the story, they're just adapting it so it's already based off an already-told story. There's nothing much to say other than praising ZUN, the creator himself.
You can watch the trailer or some of the partially found footages on lostmediawiki, an article on this matter. But other than that, there's nothing else we can do.
The legality kind of puts a lot of Touhou content out there into question, but it really is just a confusing part on Japan's copyright laws. Like the difference between an Indie & Doujin work. It's confusing to those who know nothing about copyright laws.
Heck, even if you do, Japan's obsolete copyright laws make it more complicated than it already is.