Moriguchi was remorseful

Something that's been bothering me upon reading through the board is that many seem to assume Moriguchi is entirely remorseless and emotionally cold to what she's done.

She isn't on the inside; she only forces back the emotion. In the scene where she is in the restaurant talking with the girl, a young child walks up to her and gives her a sweet. When she's later walking home she takes a look at the sweet, is overcome with emotion and breaks down crying - most likely over both her lost family and it can be assumed over the revenge route she's taking (justified by the ending). Eventually she stands with a grimace, almost half-grins and mutters "fool" to herself for letting emotion take over. She's clearly been training herself to do this as a coping method.

In the final scene she nearly breaks down again when looking at the sobbing Shuya. The realisation of what she's done gets to her and she also feels the sudden emptiness of a revenge come full-circle. She can't start again herself like she instructs Shuya to - the legal and emotional consequences of her actions await, even if she did save all those students.

She once again seizes control of herself, grins and successfully forces the emotion back. She sees the irony in her telling Shuya to start over again - who am I kidding? I expect the thinks. He'll never recover from that trauma. "Just joking".

Moriguchi grins and forces her emotion back; washes it all away, as a coping method to help her keep her cool during a long-winded revenge plan that she cannot easily back away from once started.