I don't care what happens after this; come what may
A set phrase expressing a resigned or defiant attitude: whatever happens after this point is not my concern. Often used when one has done all one can or when abandoning responsibility. The fuller form is 後は野となれ山となれ.
See also: 後は野となれ山となれ (あとはのとなれやまとなれ)
I've done everything I can. After this, I don't care what happens.
He said 'come what may' and abandoned the plan.
Literally 'let it become fields, let it become mountains'. The phrase evokes an image of land returning to wilderness, implying that the speaker no longer cares what becomes of the situation.