A person's mind is something that can be quite fragile, particularly if the person happens to be a cutie in a Crapsack World. The iconic fragile thing in fiction seems to be glass - very shiny and very fragile. This leads to it and its shattering being used as a metaphor for an individual's broken sanity. A popular variant of this is the House of Broken Mirrors.
Examples:Anime and Manga
- Occurs during Asuka's Mind Rape in Neon Genesis Evangelion at the end of a repeated montage.
- Played with in Yu-Gi-Oh!, where the Other Yugi shatters Kaiba's mind after defeating him at the end of the Death-T arc. In this case, it's intended to give Kaiba a chance to regain his sanity as he puts the pieces of his mind back together.
- One very well-known literary usage is in The Glass Menagerie, where the glass unicorn's horn breaking off symbolizes Laura's breakdown upon discovering Jim's engagement.
- One of the most frequent images in Sucker Punch is a glass breaking, once just before Babydoll's sister dies (From a light source) and the second time when Blondie dies.
- In Narbonic, Dave's glasses crack near the end, symbolizing his descent into madness.
- Avatar: The Last Airbender: Azula's Sanity Slippage culminates in her destruction of a mirror while preparing for her coronation. Her real Jerkass Woobie persona is revealed in full at this point.