What does 12 and 7 mean? I don't understand that part of Tokyo Ghoul.
The numbers allude to tarot cards, usually the Major Arcana cards. Ishida slips them in as part of the drawings to add symbolism.
For example, the “12” I was mentioning before is this:
The number 12 refers to the twelfth card of the tarot cards, which is “The Hanged Man”. The card itself can symbolize many things, but in here, it can represent the following below in bold:
Sacrifice — Letting go — Surrendering — Passivity
Suspension — Acceptance — Renunciation — Patience
New point of view — Contemplation — Inner harmony
Conformism — Non-action — Waiting — Giving up
Ultimately Kaneki “sacrifices” himself by going to Anteiku to help, because he knows there’s a good chance he won’t make it out there alive. Even more interesting is how the Hanged Man represents resurrection, or coming back to life after death. And look who pops up as the protagonist in TG:re ;)
The 7 is found in chapter 137:
The seventh card is the Chariot, which can represent some of the following:
Conquest — Honor — Victory — Energy
Egocentrism — Self—confidence — Conviction — Anxiety
Willpower — Self—assertion — Hard control — Discipline
Inflexibility — Success — Wealth — Recognition
Impulsivity — Command — Bravery — Pride
The Chariot basically represents war, perfect for the upcoming battle between Kaneki and Arima. There’s more to it than that though. The Chariot is often accompanied by a picture with a charioteer pulled by two sphinxes or horses, with each creature black or white. It’s interesting because Kaneki is often covered in black, while Arima is wearing white. They may be on the opposite sides, but they are similar in many ways.
Keep in mind that I didn’t really go into detail, there’s other analyses that people did that go into much more specifics of the tarot cards and their interpretations.