Mayumi's Somnium, PSYNCIN' IN THE SUSTaiN, is heartrending. We see how much she's had to struggle, with Ota's brattiness and their financial troubles leading to her husband's death by overwork. In the end, her Somnium turns into an endless black void in which she's left sobbing all alone, begging Ota and Takero to not leave her. Thankfully, it turns into a Heartwarming Moment in the end, when we finally get a happy memory of Ota and Takero's Mother's Day gift to her.
Aiba's Heroic Sacrifice in the True Ending. Pretty much everything about it, but most notably how torn up Date sounds as he issues the second layer self-destruct command: Telling a lie.