The two have only two interactions together, one of which happens off-screen. However, Tsumugi grows a strong hatred for Rantaro, calling him an edgy normie, and feels disgusted by his actions. Meanwhile, Rantaro's opinion of Tsumugi is unknown.
In the nails painting scene, Tsumugi watched the two of her friends, Kaede and Rantaro, having a scene together of Rantaro painting Kaede's nails and Tsumugi watched silently while becoming disgusted and tried to hide her hatred from Rantaro trying to interrupt them by offering to paint Kaede's nails. Tsumugi said that Rantaro should have blown up forever since he was being a total normie.
It was later revealed in Chapter 6 that Tsumugi was the one who killed Rantaro and framed Kaede for the incident. Tsumugi didn't want Rantaro to discover the secret and exposed of her being the Mastermind. She was aware that Rantaro, guided by his talent would be in her way and cause trouble along with Kaede who was able to unify everyone's heart, so she decided to kill both of them in the same case. Tsumugi stopped Rantaro by killing him from behind and hid the ball that Kaede rolled down the vent.
The ship sailed with the nail painting scene with the two and Kaede Akamatsu. Some fans interpreted Tsumugi's annoyance with Rantaro as her being jealous of the attention he gives Kaede in the scene. With the reveal that Tsumugi was Rantaro's actual killer, a lot of shippers abandoned the ship. However, it was still popular with those who tend to ship victim-killer duos. In certain scenarios, it resulted from "Pair the Spares" reasoning.
As it's implied that Tsumugi participated in one more killing game, some fans like to theorize that she may have been a regular participant in the 52nd killing game, the one in which Rantaro participated in before V3. They also like to theorize that the two could have been in relationship during that season.
It is one of the most written ships for both characters on Archive of Our Own. Although it's a fairly popular ship for both characters, especially for such minor one, it still loses in popularity to Amamatsu, Amasai, or Oumami.
Fan arts often tend to reference Tsumugi's crime of killing Rantaro. Some also tend to show the two together as a sort of accomplices, referencing Rantaro's role as a major red herring.
- Rantaro Amami/Tsumugi Shirogane tag on AO3
- Rantaro Amami & Tsumugi Shirogane tag on AO3
- Shirogane/Amami tag on FanFiction.Net
- Rantaro's relationship with Tsumugi on Danganronpa Wikia
- Tsumugi's relationship with Rantaro on Danganronpa Wikia
- This is one of several Danganronpa ships between a victim and their killer, with the others being Leosaya, Chimondo, Yamaceles, Twoteru, Mahpeko, Tsumionji, Band Aid, Nekodam, Komanami, Snatsumi, Nishichino, Amamatsu, Tojoshi, Shinnaga, Tenkiyo, Gokuiru, and Oumota.
- This is one of two ships between Rantaro and his culprit, with the other being Amamatsu. However, in this case, the person he's shipped with is actually his killer.
- Tsumugi stands next to Rantaro's portrait during the Class Trials in New Danganronpa V3: Killing Harmony.
- They're together on one of Danganronpa V3's Steam cards, the one titled "Truth."