Though they were already shown to speak to one another before, Sonia and Gundham's friendship truly blooms during Chapter 4 after they finished the Roller Coaster ride and Sonia asked to accompany Gundham on a trip to an amusement park in hell. They became very close due to their complimenting interests (such as Sonia's interest in the occult with his odd behavior, or her liking of his "cute hamsters"). Sonia showed interest in Gundham's hamsters multiple times, which successfully flustered Gundham and made him blush.
She constantly sides with Gundham, even going off with him to explore the Fun House before Kazuichi Souda noticed. In the main story, Sonia is also the only one who has made Gundham blush. It's implied that they have a romantic interest in each other, much to Kazuichi's annoyance.
Sonia is also the only one that Gundham does not refer to as kisama (a way of saying 'you' that suggests contempt, or alternatively an archaic polite form of 'you') or by their last name, instead calling her "she-cat" at one point or "the Dark Queen", which is mentioned to be his fantasized version of Sonia. He claims that the Dark Queen has great power, which has not been awakened yet.
When Gundham is deemed the culprit of Chapter 4, Sonia refuses to believe it, urging him to object against Hajime's accusations. Gundham did defend himself but was unusually silent, and Sonia begged him to say something many times. She also pleaded with Monokuma to save Gundham from his execution, but finally let Gundham go after she was convinced by Gundham himself. He told her actions were "unbecoming of someone of your status".
Gundham's Four Dark Devas of Destruction are entrusted into Sonia's care after his "death". After Gundham's execution, Sonia has a new resolve to make it out alive without any more killings because of his last words about not giving up.
During their time at Hope's Peak Academy, Sonia latched onto Gundham's eccentric personality when Chisa Yukizome left and the two bonded. Sonia enjoys the occult and she appears to like the Four Dark Devas, calling them cute. She is shocked when Gundham refers to her as a low ranking demon.
After Gundham returns from his coma and the former Remnants of Despair finish assisting the Future Foundation, Sonia is seen eagerly talking to Gundham on the ship, admiring his hamsters.
Behind the Scenes
Kazutaka Kodaka's favorite scene from episode 5 of Despair Arc is when Sonia and Gundham combined together to greet Chisa upon her return from her probation.
While Sonia and Gundham are shown to be close friends in DanganRonpa, some fans feel their interactions might mean they have romantic feelings for each other, especially Gundham, which can be seen when Sonia's words make him blush. This ship rivals Sounia, as Kazuichi likes Sonia. There are also some fans who love both ships equally much, thus creating Sonsoudam.
- Sonia/Tanaka tag on AO3
- Tanaka/Sonia tag on FanFiction.Net
- Sonia/Gundham tag on FanFiction.Net
- Neko_Nessa's Sondam Fanfiction
- Gundham's relationship with Sonia on Danganronpa Wiki
- Sonia's relationship with Gundham on Danganronpa Wiki
- In Danganronpa V3 bonus mode, Gundham thinks that Sonia is performing a demon ritual but she tells him that is simply cleaning. Sonia tells Gundham that she couldn't hang out with her friends in her old country like this.
- Gundham's stage actor, Masahiro Inoue, was married to Sonia Nevermind's stage actress Jamie Natsuki, but as of June 2020 they are officially divorced.
- Sonsoudam refers to the ship between Sonia, Tanaka and Kazuichi Souda
- Sondhime refers to the ship between Sonia, Tanaka and Hajime Hinata