The two have never interacted in canon, however they do share an event in Danganronpa V3's bonus mode, Ultimate Talent Development Plan.
In the event, Tsumugi asks Sonia if she wears gorgeous dresses and tiaras in her country, Sonia confirms she does. Tsumugi says that she bets they're beautiful and well made, and that she would like to see them, and says she bets they're a perfect reference for a cosplay. Sonia then asks Tsumugi if she would like to wear them, in which Tsumugi insists that it was okay, because the dresses were too glamorous for her, and tells Sonia that she only cosplays fictional characters.
Sonia then asks if cosplay is dressing as fictional characters, Tsumugi confirms it, and says that it lets her become someone totally different and live in a different world. Sonia says she understands wanting to be a different version of herself, and Tsumugi asks if Sonia would be interested in cosplay, Sonia denies but says that she wanted to become a normal girl. Tsumugi then says that princess Sonia and student Sonia are the same one, and Sonia responds with “For that, you have my utmost praise!“ Tsumugi says she's very grateful. Tsumugi then says that the aura of a princess is powerful, Sonia responds that Tsumugi was a delightful person, Tsumugi then responds back the same thing to Sonia too. Tsumugi says she feels plain near someone as sparkly as Sonia. She also says that is plain to see they get along well, Sonia agrees and says she was hella down to hang out with her anytime and calls Tsumugi her soul sister.
The ships sailed due Sonia's and Tsumugi's good friendship, that both developed, in the Ultimate Talent Development Plan.. Due both Sonia and Tsumugi being very compatible with each other, many began shipping them togehter, a popular headcanon is that Tsumugi would cosplay as Sonia in her Princess Dress, like in the famous Barbie: The Princess & the Popstar Movie. Another headcanon is that if the Killing Game didn't started and Sonia and Tsumugi would have meeted in canon, Sonia and Tsumugi would have been Best friends, due their similarities. Noneless, the ship is considered a rarepair, or even a crackship to most due to both of them having much more popular ships, such as Sondam, and Kaemugi.
- Both have long hair and blue eyes.
- They both are 5'7" and have almost the same weight.