I never said this, but Okita has a horrible backstory. I'm still working on it but to sum it up, his parents were killed by poachers when he was merely a kit. He blames himself for their deaths which lead him to never rely on anyone, as he doesn't want pity from others.
Ontop of that he has tuberculosis.
In his world, true happiness is a myth and usually wants to die.

#OkitaTsukino