Spirit Trio

Spirit Trio is the friendship between Angel/Doro/Tenshi, Anobasu/Bus, and Nisch from the TUYU fandom.

Canon
In "If there was an Endpoint." it is revealed that alongside the some of the other girls in the TUYU universe, Anobasu and Angel went to the same school. It is unknown if they have ever interacted. Later, Angel is seen walking with Damo, who is a character highly speculated to also be Nisch, or at least knows Nisch. Angel is an Angel, and Nisch is a devil, while Anobasu has angel symbolism and is dead. All three of them have been drawn in official art together at least once.

Fanon
Spirit Trio was regarded as a trio due them being drawn together in official art. However, the relationship between Angel and Nisch, Doronisch has a lot more attention than the three of them together.