Broken Gate

She vowed to never open that gate, never again. However, no one said fate would be kind

—AO3 Summary

Broken Gate is a novelette by Amoridere.

Two hundred years after some unspecified event, Toramaru ("Tora") goes looking for his lost sister, Nezumi.

Tropes used in Broken Gate include:

Adaptation Expansion: The story, according to Amoridere, was based on an eight-page poem.
Barrier Maiden: Nezumi is the guardian of the titular gate and, towards the end, she is sacrificing her strength to delay it reopening.
Big Brother Instinct: Played for some tragedy. From what we can see, Tora and Nezumi were pretty close but what makes this worse is that, in Chapter 11, he can feel her dying and there isn't anything he can do.
Blood From the Mouth: A weakened Nezumi in Chapter 14.
Broken Bird: Nezumi in, as due to her situations and the events that came before, one could say she's become emotionless (right down to feeling) would be because her situation removed her ability to cope with them otherwise. However, chapter 17 implies that she was this long before.
Color-Coded for Your Convenience: When the story was on taskey.me (when the website used to exist) has the dialogue of the characters highlighted in different colors.
A Dog Named "Dog":
- We have the following Japanese names for characters; Nezumi (rat or mouse) a rat youkai, Ryuuji (dragon) a dragon youkai, and Tora (tiger) being a tiger. Miyako is the Odd Name Out, as her name isn't necessarily an animal one.
- Kagami is really that, a mirror-opposite reflection
Downer Ending: Or, possibly, a bittersweet one. Shortly after resealing the gate, Nezumi dies, feeling her emotions again for the first time in over 200-years, and her death is the last time her siblings, Tora and Miyako, see her again.
Eastern Zodiac: Nezumi (rat), Tora (Tiger), Miyako (horse), and Ryuuji (dragon)
Emotionless Girl: Nezumi really seemed to have mastered suppressing her emotions in light of her situation, as examined in chapter 4, when it's noted that her lament doesn't feel painful (like it would for some), instead, it feels cold. It's to such an extent that she wished she could cry or, at least, shed tears, something to express her anguish in some way. Likewise, she hadn't felt cold in a long time, either, and is very detached from her own thoughts towards it. Naturally, her feeling lament for the first time made her realize how her pragmatism had its drawbacks in that she had shut her mind off to anything irrelevant to guarding the gate, her thoughts and feelings included, in which case she stopped feeling them.
- To some extent, six chapters afterwards, this becomes a bit more extreme, as when she starts to feel the aforementioned again, she decides to, as the story put it, "destroy" that feeling and doesn't feel it again for the remainder of the chapter (a move called disaffectation). The reason as to why she does this was because she couldn't cry, thus, she refuses to allow herself to feel them once they come, as, if she cannot express them well, then there isn't a purpose in feeling them, almost invoking this trope more directly. In short, she would much rather be emotionless and not to feel emotions vs not being able to express them. When she finally does feel her emotions, it's when she's shedding tears as she dies.
Emotions vs. Stoicism: Nezumi suppressed her emotions to the point she couldn't feel them anymore, as, whatever wasn't related to guarding the gate got ignored, however, if she could feel them, it would probably make her situation worse.
Flower Motifs: Lycoris flowers, the which are related to Nezumi and her rather bleak situation considering that she dies in the end, the which being foreshadowed by it being mentioned that she had them growing around her home, her minion bringing her siblings a lycoris flower and their grief, and, not too long before her demise, she gathers up a large group of them and replants them around the titular gate.
Foreshadowing: We have Miyako's "GO! Go and never return but, remember, if you seek her out, then you will have killed her." and the fact that Nezumi's living arrangements are dismal and her Floral Motifs being lycoris flowers.
Forgiveness: Somewhat a theme, considering that Nezumi did offer it to her brother Ryuuji despite having been abused.
I'm Cold... So Cold...: The story plays with this in Nezumi's case. While she isn't dying until much later, a sign that she's not long for the world is when she has a twinge of feeling anything (being emotionless). The closest thing she feels to the pain of lament (besides numbness) is cold and it says something if she hadn't felt cold up until that point either.
Karmic Death: Ryuuji's. With him being something of a Jerkass and being Too Dumb to Live, he had that a long time coming.
The Man in the Mirror Talks Back: During an inverted case of The Mirror Shows Your True Self, Nezumi talks to her reflection, said reflection being the first to address her. However, her reflection, later named "Kagami" by the narration, is a manifestation of her (autonomous) madness, explaining why she acts the way she does. When Nezumi destroys the mirror, her reflection is freed, leaving her alone.
The Mirror Shows Your True Self: In chapter eight, this is inverted, as the mirror doesn't really show Nezumi's true self, actually, as Nezumi's reflection is the opposite of what she is, right down to being more emotive. The reason for this because said reflection is a manifestation of her madness, the which she talks to.
Mirror Self: Kagami may be Nezumi's reflection but she's the total opposite of what Nezumi is.
Noodle Incident:
- A Played for Drama example. At first, it wasn't made clear what happened 200 years before the main storyline but, we do find out that, years ago, Ryuuji was quite abusive to his younger sister, Nezumi, and, in retaliation, she cursed him. Well, instead of accepting the forgiveness she offered (something needed to lift her curse), he antagonizes her further, which caused her to open the titular gate
- The titular gate. It's not really clear how or when it came into existence, just the fact that it's there.
Onmyodo: Apparently, Nezumni is an omnyouji, the which is implied in the fact that she's sealed away something powerful behind a gate and has to reinforce those seals, along with placing a curse on her older brother.
Rage Against the Reflection: Nezumi, doesn't feel emotions as she shatters the mirror, however, the narration calls her actions out of "an annoyed rage".
The Stoic: It's implied Nezumi was this before she became full-on emotionless. Miyako doesn't remember the last time she emoted, just that, quote, Nezumi's "tears dried years ago".
- Not So Stoic: Or, in this case, "Not So Unfeeling", by a certain point, Nezumi starts to feel something that could be best described as "lament"
Swarm of Rats: Happens twice:
- The first time this happens is in chapter seven when the rats look like they're having a funeral procession and that comes with mowing down everything in their way
- The second time is chapter thirteen and the rats act like piranhas with the narration and her siblings wondering if Nezumi's minions are expressing the "rage she didn't possess".
Too Dumb to Live: Ryuuji, a total bastard, as per flashback, decided to antagonist his sister, Nezumi further, despite her offering forgiveness, nevermind the fact that she placed a curse on him for treating her so poorly, which wasn't a very good idea to start with, as she is an omnyouji and a powerful one at that, along with the fact that he's the reason that she had opened the gate in a fit of retaliation. Later in the story, he decides to antagonize her again and, unsurprisingly, while she's dying, she breaks the seal, opening the gate, and whatever was sealed behind had swallowed him, ending his life once and for all
Tragic Dream: It's mentioned that Nezumi wanted to live quiet and contently. Unfortunately, as we can see, her life wasn't anything like she wanted.