I'm continuing to try and fully understand the OPs in Jujutsu Kaisen, and right now I'm interested in knowing whether, in the first OP, there is any deeper significance behind Itadori Yuji riding an empty metro train half-asleep while being knee-deep in water.
I suppose the scene is vaguely unsettling simply because of the way the everyday act of riding a metro train is shown to interact with the supernatural — the knee-deep water filling the train, which is empty except for Yuji, who is somewhere between wakefulness and sleep. But, what is the symbolism behind the water filling the train, specifically?
Curiously, near the very end of the OP, one of Ryomen Sukuna's fingers is shown sinking into the water, and a plant is shown to sprout from it as it sinks deeper.
Sukuna's fingers are an integral plot point, that much is fine. But why does a plant grow rapidly from the finger when it enters the water? What is this meant to convey?