Spring Summer ..variation (spoiler)

I found it interesting to see the 4 season motive in this movie too.
When she performs for him in the prison, the 4 seasons also predict the rythm of their relationship with a beginning, highlight, decline and ending.

When it is winter, she must leave and he will die.
Through the seasons, their shared part of life, she revived his soul and thus gained her already dead soul back.