There is... a lot to say about Ave Mujica. But I would rather split that into the things that I liked, and the things I disliked.
Things I liked:
Visually, this show is gorgeous. I thought MyGO!!!!! looked amazing, but this show just takes it to another level. Nearly every scene in this show is wallpaper worthy.
The characters that get a significant amount of screentime are wonderful as well. Sakiko, Mutsumi, and Uika are up there with the best characters in the entire AveMyGO series. The development and growth they experience throughout the show is incredible, especially Mutsumi's.
If I had to choose one thing to praise about the show above all else, it would be the music. The original music in the MyGO!!!!! anime was incredible. The music in the Ave Mujica anime is above even that. The instrumental work is excellent and Sasaki Rico's (Uika) vocals are absolutely beautiful. The instrumental work from Akane Yonezawa, Mei Okada, Yuzuki Watase, and Kanon Takao is incredible as well.
The show definitely expects viewers to be familiar with the story of MyGO!!!!! and it serves the plot incredibly well because of how important the characters of MyGO!!!!! are to the stories of the members of Ave Mujica, especially for Sakiko and Mutsumi due to their connection to CRYCHIC.
The story itself is incredibly original. The show isn't afraid to tackle dark topics and it tackles those topics with tact and care, and in the end is all the better for it. Sakiko especially is an incredibly flawed person, but that makes her all the more relatable to the audience. She's selfish and often makes poor decisions, but in the end, I can't help but love her especially for all the growth that she experiences during the show.
Things I disliked:
The pacing of this show is extremely bizarre. Episode 1 focuses heavily on plot points set up in MyGO!!!!! and is largely fine for the pacing, however it gets really weird soon after that. Episodes 2-10 focus EXTREMELY heavily on Mutsumi and her issues, which is great for her character as well as Sakiko, Tomori, Taki, and Soyo's arcs because the five of them are tied together by CRYCHIC. The issue with all that is that Ave Mujica has three other members: Umiri, Nyamu, and Uika. Nyamu gets a decent amount of focus, but not nearly as much as the other characters. The issues begin to arrive when it comes to Uika and Umiri, who get very little screentime throughout the first two thirds of the show. After episode 10, episodes 11 and 12 are almost entirely focused on Uika, and her story is great! But Umiri has very little stuff happening around her. Her arc is built up and "resolved" over almost just one episode.
Episode 12 is also incredibly messy. Since episode 13 is pretty much all a concert (and an incredible one at that) episode 12 has to try to "resolve" all of the issues plaguing the members. The issue, however, is that all of the character's issues are swept under the rug and pretty much ignored. On top of that, the main conflict of the episode (and Uika and Sakiko's arcs) are solved with incredible ease. The show is far too short for what it was trying to accomplish and I truly believe that this episode makes that clear more than anything else.
In Conclusion:
Ave Mujica is not the most tightly written or most impressive show ever made, but it is extremely entertaining. The drama is great and most of the characters are incredible. If you're looking for a tightly written series, this is probably not what you're looking for, however, if you want a series that will make you FEEL the struggle of the characters and get you to sympathize with their problems, this show is incredible. Also, it has Mutsumi Wakaba. And she is just... the best.
