Nagitsuba

Nagitsuba is the femslash ship between Nagisa Tsukimiyama and Tsubaki Aoyagi from the D4DJ fandom.

Canon
RONDO BAND STORY ONE

The two first appear together in Rondo's First Band Story, in Episode Six, titled "Wallflower," when Nagisa watches Aoi approach Tsubaki to invite her to be in the band. This doesn't go well, as Nagisa notes that Aoi made it sound like she was hitting on her - which resulted in Tsubaki leaving.

In episodes Seven and Eight, they have brief moments together, between Tsubaki watching Aoi, Hiiro and Nagisa preform and Nagisa and Hiiro spying on Aoi and Tsubaki as she sings. They only properly meet in Episode Nine: "Yet So Alike." Nagisa has invited Tsubaki to a cafe to introduce herself and try and push Tsubaki in the right direction. She questions if Tsubaki is ready to 'take the plunge,' and accept Aoi's offer, emphasizing that anything less than her full effort won't cut it. She bookends this statement by saying that's exactly why Aoi had approached her, implying that she thinks Tsubaki isn't someone that wouldn't do something half-heartedly. She proceeds to ask if Tsubaki's 'story' has begun, telling her that her own story only began when she got on stage with Aoi and Hiiro. Before Tsubaki can respond, the food Nagisa ordered for both of them arrives, and she closes the topic of conversation by saying she's not the one Tsubaki needs to talk to.

In Episode Eleven: "Phosphorescent Glimmer Awakens," after Tsubaki has joined the band, she comments on Nagisa, Hiiro, and Aoi's banter, stating 'You all get along so well." Nagisa responds "You all? You mean we, right?" which leaves Tsubaki touched as she reveals that she's very glad RONDO is the four of them. Nagisa is ecstatic over this confession, and pulls her into a tight hug, which forms into a group hug after Hiiro and Aoi join in.

In Episode Thirteen: "The Seeds Of Doubt Bear Fruit," after the previous vocalist for RONDO, Yuki, insists that she still wants the spot Tsubaki has taken, Tsubaki is left shaken up. Nagisa notes that it was "Rater presumptuous of her [Yuki]." and that she was just trying to get rise out of Tsubaki. Unfortunately, RONDO's words of encouragement aren't enough to make Tsubaki sure of herself. Nagisa is aware of this, and mentions to Hiiro that there's definitely something wrong. In Episode Fourteen: "Gotta Get Away," Tsubaki observes that Nagisa has sent her multiple messages since her disastrous performance at Music Crown. This leads us to a flashback that seemingly takes place right after the performance. Masaki informs Aoi, Hiiro, and Nagisa, that Tsubaki wanted to say a proper goodbye to them. Nagisa, shocked and upset, loudly exclaims "Are you planning on quitting, Tsubaki?! We just got started!" Hiiro tries to interject and calm her down, but Nagisa continues, begging "But...! You promised! The four of us are RONDO! Of course, you need your rest today, but...once you're better...!" Tsubaki responds to this with an apology, which Nagisa follows up by saying it's not her fault and that she doesn't need to apologize. She calls on Aoi to say something, but Aoi just apologizes.

In Episode Sixteen: "Reigniting the Torches," while Tsubaki is having dinner with the rest of RONDO, she says she doesn't plan to go back to singing. Nagisa says she understands how she feels, telling her to not use her feelings about them as an excuse, and that only she can decide if she wants to sing or not. Tsubaki repeats that she's not going to. Nagisa blurts out "If that's your decision, then it's fine. As long as you can live without singing anymore." Hiiro tries to explain that Nagisa didn't mean to be harsh, but Tsubaki leaves anyway. Nagisa seems to regret her blunt wording, staring after Tsubaki sadly.

In Episode Seventeen: "Sparks Gather Into a Roaring Blaze," Aoi, Hiiro, and Nagisa go after Tsubaki, with Aoi arriving first and convincing her to rejoin the band. Nagisa is relieved, and tells Aoi that she should've just been honest to begin with. Hiiro reminds her that not everyone is as single-minded as she is. When Tsubaki confirms she's going to stay in the band, Nagisa assures her that she "never expected anything less." Tsubaki says she's looking forward to being back on stage with RONDO, and Nagisa bashfully admits that she is too, and that she can't wait to play while Tsubaki sings.

In Episode Eighteen: "All of the Lights will Shine Anew," after Tsubaki starts apologizing for everything again, Nagisa tells her she doesn't have to apologize anymore, and that "It's okay to worry about things, but talk to us, okay? You don't have to suffer on your own." She then quietly adds "Together...the four of us are RONDO." Hiiro calls her out on her shyness, and Nagisa responds that, unlike Aoi, she's not used to 'this kind of thing.'

In Episode Twenty: "Toward the Next Score; Still Unwritten," after RONDO's comeback performance, Aoi mention's Tsubaki's opening speech, which Nagisa says gave her goosebumps, and made her think "Our vocalist is the best!"

Fanon
Nagitsuba is not a very popular ship in the D4DJ fandom, which can be explained by the abundance of canon content for other RONDO pairings. Namely Tsubaoi and Nagihiiro, both of which have adequately large fanbases.

That being said, there has been a small uptick in attention towards the pairing due to their interactions in both RONDO's Second Band Story and also their joint event, "Because We Can't Play It Alone."

Fandom
Nagisa/Tsubaki tag on AO3

なぎつば posts on Twitter

なぎつば tag on Pixiv

Trivia

 * In Nagisa's introduction story, when asked to talk about someone in RONDO, she says "Well, ever since I first heard Tsubaki's songs, I've been hooked. Oh, but don't tell anyone. It's embarrassing."
 * Though unproven, there has been a long-running rumor that the song Ultramarino Flor Seca was written to be a song from Tsubaki to Nagisa.