I was almost 100% positive the series would move towards a great or maybe perfect conclusion. After this episode I'm not so sure any more. This episode was a mixed bag of good and bad.
The most obvious flaw was the directing. Some transitions were truly confusing and suddenly the few still screens in the middle of the episode(?). I hoped we could get some hints as to what Bu-chan actually is, but I'm afraid we will have to settle with the comic relief power-up/transform sequence. Although I was sort of glad to see they didn't try to go full on serious in the last few episodes, but maintain the comedy aspect as well.
The showdown with Mimi has thus far been quite good. The traversal of the various Pure Illusion worlds makes sense given the setting. Ending up on the place where the "real" Mimi resides in order to snap Cocona out of it was expected. Also, Yayaka transforming finally happened
But that is were the showdown fails. If they wanted to play it safe they should have made Mimi too strong to beat even with Yayaka transforming and both of them falling into despair (the memory alteration was a good moment for that) and end the episode there as cliffhanger. Obviously they would need all three transformed to beat the "bad" Mimi and to achieve that, the external device (Salt and crew) would trigger something inside Pure Illusion.
But no, we simply get Cocona getting a little motivational speech from her "real" mother, Papika getting her memories restored (completely removing the impact of the memory alteration scene) and together defeating the "bad" Mimi. It didn't even require all three of them, making Yayaka only useful for transporting Cocona to Pure Illusion (which arguably was thanks to the "real" Mimi in the shape of a fragment Yayaka carried around).
At this point I fear what the next episode will bring us. Nyunyu and that ELPIS (?) thing have not had any action yet. So I guess this wasn't really the end of the "bad" Mimi and/or Pure Illusion turning against them. The device/thing would probably serve as some 'deus ex machina' and Nyunyu will be nothing more than a plot device for activating the device and/or moving it into Pure Illusion. Let's just hope we get a better conclusion than this, otherwise it would a bit disappointing end to an otherwise great series.