This is a series with 7 light novels as of now, and only 11 episodes of anime. This probably explains why the anime felt crowded with Loads and Loads of Characters that it simply wasn’t handling very well.
The premise is interesting enough: an artificial island with “ruins” containing pieces of Nanana’s collection of powerful artefacts, a main character exiled to the island by his family, oh and Nanana’s ghost living in the only apartment that Juugo Yama can afford.
Nanana was murdered in that apartment 10 years ago, and can’t move on until her killer is found. In the meantime Nanana can’t leave the apartment, will only eat pudding, and plays computer games 24/7.
The “ruin” sequences are generally well realised, and can be quite exciting to watch, but the multiple layers of mysteries and enigmas felt incomplete.
As if these were just signals for readers of the light novels to fill in the blanks. This is not something I enjoy seeing when watching anime.
As mentioned before there are too many characters, although the “master detective” Tensai is huge fun to watch.
Despite the issues each episode is individually entertaining, and the final episode delivers a strong piece of character work between Nanana and Juugo.
So far as I know a second season hasn’t been announced, but I’d probably watch it if only to see if I could start making sense of the story.
Overall Nanana’s Buried Treasure is entertaining enough to overcome its flaws (just), but not much more than that.
I’ll wrap this up with the OP, which is the best OP of the four shows I’ve been watching this season.