Main characters: A male rabbit-like black and white creature who is a botanist. He has a plant in his room and takes a good care of it everyday like it's his best friend.
A female version of the rabbit-like creature who lives on the same floor as him. She is also a botanist. The boy loves her so much that he took a part of his precious plant and gives it to her as a present.
Setting: An developed country with huge population / near future (1-2 centuries later)
Conflict: person vs. nature
Climax: When the jellyfish take in the boy into its body.
Symbols: plant--pureness
growing balls--mysterious, new, scary
grey and black building--destroyed part, there's no going back
black smoke--death, illness
fluff--happy, joyful, warmth
one remained tree--hope
water--living source
jellyfish--savior
red--danger
Theme
Protect the nature if you don't want this to happen. (destroyed city, polluted air, people getting sick from disease caused by the environment)