In chapter 14, Shut Hell explains that she can't let go of her grief, since she's the only one left to remember her comrades. She then takes interest in Yurul's writings, asking if he can write some names (those of her friends). Upon reading the written names she realizes that even if she were to die, the words won't vanish, and will not forget her comrade's names. As she reads the words over and over, she remembers memories of her friends, and tears up, since earlier she couldn't even remember their faces.
The entire conversation between Yurul and Shut Hell in chapter 18 is both heartwarming and tear-jerking. Yurul is desperately trying to save Shut Hell even though they both know he doesn't have the strength to break her out of her cage. But she's not angry or mad, only happy to see him better again, and relentlessly comforts him, going as far as to say that he shouldn't blame himself for her current predicament, since he made her see that her life was being consumed by seeking death. He bitterly complains that he wanted to share so much more with her, and that his 'nice words' are going to kill her, but she denies this, stating that he gave her back her life.
"Don't cry, Yurul... Thank you. Whether you can protect Taika's legacy or not, I love you. [...] Go now. Your song will always be with me."
The subsequent revelation that the strong bond between them is what allowed Sudou and Suzuki to remember about them is completely heartwarming.