Why Is This So Unbearable? is the title of the twelfth episode of the Magia Record: Puella Magi Madoka Magica Side Story anime.
After Touka says that she has no memories of Ui, she explains to Iroha and the rest of the group that a magical girl's Soul Gem contains their literal soul. Momoko and Kaede reveal this news to Rena.
Mifuyu reveals her memories to Iroha which shows that Kanae, Yachiyo and Momoko in fact perished after her Soul Gem was shattered. After this, another ally named Mel transformed into a Witch when their Soul Gem was overcome with despair. Overall, the magical girls realized they had been deceived by Kyubey.
Feeling the despair from this knowledge alone, Mifuyu's Soul Gem becomes contaminated. However, rather than being changed into a Witch, a Doppel is created instead. Touka reveals this was done to offer magical girls liberation.