It's a bit of a Guide Dang It to trigger, but in Chapter 4, a secret scene involves Naomi breaking down due to Seiko's death...only for Seiko's ghost to appear and comfort her. Seiko assures her that she will always be with her in spirit, and asks only one thing from Naomi; a kiss.
At the end, Naomi discovers that she was the one who killed Seiko while being controlled. How on earth does she not immediately succumb to the darkening, you ask? Well, at the very end, when she admits what she learned out to Satoshi, we find out: As Naomi was falling into the depths of despair, she received a text from Seiko. The same text Seiko intended to send to Naomi before she died, apologizing for their fight. Naomi didn't understand why she got the text at that moment, nor did she care, convinced that Seiko died hating her. She receives the same text a second and third time. Naomi initially thought that Seiko was spamming her out of spite, until she realized that the text was titled "No hard feelings". It's enough to bring both Naomi (and the player!) to tears.
Although some people find it Squicky, the "Extra Ending" of Chapter 5 where Yuka admits that she loves her brother is touching in its own way. Even though she knows that Satoshi doesn't return her feelings, she still willingly Takes The Scissors that are intended for him.
It's rather sweet watching Mayu and Nana bond over both being the drama club after Mayu and Yoshiki save Nana's life.