Tsubaoi

Tsubaoi is the Femslash ship between Tsubaki Aoyagi and Aoi Miyake from the D4DJ fandom.

Canon
The relationship between the two is technically a central theme not only of their unit's story quest, but in fact the very essence of RONDO itself. In particular, all of their songs with multiple vocalists are officially performed as a vocal duet of Tsubaki and Aoi, even though Hiiro often sings the backing vocal line.

According to EMSS, the official lyric provider for D4DJ songs, “[Re]termination” and “Black Lotus” are confirmed to be related to Tsubaki and Aoi as a pair.

The most important source of content for their ship is the 2020 Valentine's Event, which was also the first such event in the game at all. In the RONDO Valentines event, Tsubaki is shown wanting to give Aoi chocolates for Valentines Day, however she did not want to make it average. Tsubaki decides to tail Aoi one day, in order to notice something special and personalise Aoi's chocolates. However, Tsubaki ended up feeling more doubtful, due to Aoi's popularity and her inability to go anywhere without getting noticed by fans. In the end, Tsubaki ended up making the chocolates anyway, with the help and consultation of Hiiro, reassuring her that Aoi would be happy with any kind of chocolate she receives from Tsubaki. When Valentines Day finally came, it was no surprise that Aoi received many chocolates from fans. Tsubaki again felt discouraged but eventually got the courage to meet with Aoi alone that night in order to give her the chocolates. Nervous, Tsubaki finally took the plunge and gave Aoi her chocolates. To her surprise, Aoi also gave her chocolates in return. The two exchange the gifts while flustered.

English translations have made the meaning and intent of the chocolates more ambiguous. Other dialogues experiencing the same problem with language interpretations between translations is one of Tsubaki’s menu voice lines.

”I was panicking because I forgot my umbrella, but Aoi put hers over me...We’re...sharing an umbrella aren’t we?”

While the English dialouge simply says they are sharing umbrellas, there is more romantic connotation behind the original voiceline in Japanese, stating that the 2 people under the umbrella is in love.

Fanon
TsubaAoi quickly became the most popular ship in the franchise, both due to more or less confirmed attraction from Tsubaki, and due to Aoi's status as one of the most popular characters in the game. This was also particularly helped by the fact that most of the RONDO-related events or side content is in one way or another devoted to either the interaction of the two, or at least the attraction from Tsubaki. In this regard, due to the huge popularity of the ship and the frequent teasing of the authors, anyone easy can find a headcanon that the canonicity of this ship is either implied or directly confirmed in one form or another.

Anyway, while the game itself is mostly trying to be ambiguous about it, unambiguously depicted as romantic Tsubaki's attempts to make Valentine chocolates for the Aoi Valentine Event and several episodes of Puchimiku actually confirmed crush on her part.

Tsubaki's sexuality is still unknown, as the plot or authors never commented on whether she is attracted to Aoi because of her famous handsomness or whether she is attracted to girls anyway. But one way or another, it seems that she can at least be called a queer, since she never shows even the slightest problems with the fact that she is attracted to another girl, the only thing that prevents Tsubaki from confessed directly is her shyness and lack of much social experience.

This is also associated with some controversy on the part of people who ship other pairings or aren't interested in D4DJ shipping at all, since a public expression of doubt about this ship often leads to various conflicts or even attacks. For example, the D4DJ fandom wiki even closed comments on the bot girl's pages due to the that people were constantly arguing over the ship with each other.

Trivia

 * Tsubaki and Aoi were the only characters to mention each other during the limited lines of the Valentine's Event.
 * When Tsunko, Aoi's VA, was asked to comment on one of her unit's performances on Photon Maiden TV, it was Tsubaki's VA's performance of a song from the Valentine's event.
 * Due to Aoi's refusal to speak of her life goal with a smile during the RONDO introduction video, fans often joked that her goal would marry Tsubaki.