Magia Record Story Bye Bye, See You Tomorrow ~Memories of the Kamihama Large Residential Complex~
The following is a summary posted on 4chan's /pmmm/ general by Summary Anon.
Seika made a wish to resurrect Reira who was kissed by a witch and killed herself. Reira's memories of this event are wiped off by the wish as well. Seika then fought to defend the area alone.
Reira made the wish to make up with Seika since they had a fall out when she questioned her friend's recent out of character behavior and she snapped since she did not want Mito and Reira to join her in hell. Thanks to her wish, Reira recovered her memories and confronted her friend on why she is carrying all of the burden by herself.
Mito is bullied in school since she is air-headed, thus her mom wants to move and enroll her in a new school and change the environment for the better. Since this news come together with the fact her friends have fallen out, it was a huge blow to her and she was approached by Kyubey. She had not made a wish when part 1 ends but she is questioning them why they are cosplaying and keeping secrets away from her to themselves.
Nanaka's group appears near the end where Akira suggests they should check out the area the new girls are in since there are cases of people missing occurring in frequency there. Nanaka mentions that the PM there has requested none should interfere in that area, and says PM should solve problems through dialogue instead. Kako asks her some details of this PM, in which Nanaka replies that the PM has a piercing gaze and intimidating atmosphere, though it also tells of a girl being forced to the corner with the thoughts of "This is my home, my important place."
Reira and Seika couldn't talk to each other after realizing the reasons why they contracted and kept Mito out of the loop for fear of her contracting as well. During one hunt of familiars, Reira and Seika get to the location at the same time, but couldn't fight together, resulting in Seika suffering a broken arm. They then realize the truth: their soul gems are now their vital organs and will die if it breaks. They then part with a heavy heart.
Seika went to the rooftop to cool down but is met by Mito and Reira. Mito chided Seika that she should pick up the phone and revealed that she wanted them to meet together. She surprised them by transforming, saying that she wanted them to patch up before leaving.
Her PM powers is Quantum Burst aka OO Quanta, and the three connect their hearts together, finally telling how they feel, their confusion, guilt, anger and caring for each other, making them closer and finally patch up.
Mito revealed her powers can be used by anyone, and that she tried it on Kyubey, but was greeted by pitch black. It did reveal that the clue to the witch is in Reira's memory before she jumped off the building.
After searching her memories, Reira realized she was heading to a 516 room which shouldn't exist since the tallest flat is only 15F. But since they are dealing with witches, they decide to try looking anyway.
During the search on the 5th floor of the 12th block, they found a trail of X marks, leading them to a barrier which teleports them around. As they are following the X trail, they return back to the 5th floor of the 12th block, but this time there is an extra room of 516. Inside are plenty of Xs which led to the witch.
They managed to defeat the witch, and the case is closed. Reira and Seika are glad to know Mito will be just moving to another portion of Kamihama, so they can still catch up easily. They found a 4 leaf clover together and Mito moved with a smile.
The epilogue shows that they are still hanging out together and even closer since Mito's powers is just connecting people's hearts, no brainwashing, no altering of anything, so as long as you are willing to talk, you will be found.
It ends with them meeting Konoha and her sisters during a witch hunt and they introduces themselves.
The awful truth:
Mito, Reira and Seira discovered that it was room 515 of block 12 where the family disappearance occurred. From the homepage of their community, they saw videos of different celebrations held there, and one features the daughter of the missing family, representing the children of the area and giving an opening speech. With a bright smile, she talks about how she loves the place and that she loved it as her home and important place.
Piercing these clues together, we the players can tell that the girl is the PM Nanaka met up with whom rejected her offer to help. She became a PM to deal with the witch, but she failed. Her family and herself are caught in the barrier and perished (bodies disappear in barriers), thus explaining the sudden disappearance of the family. If she had accepted Nanaka's help, then everything might be different.
It either ends with Reira not contracting, hinting that Seika is going to die on her own since she is so new that she broke her arm fighting familiars, they never manage to make up and the gap will never be filled or they failed to find the witch, hinting on more missing cases and their eventual defeat.