Yes you can lighten your dark inner thighs in a week using coconut oil and lemon juice.
To use lemon juice and coconut oil to lighten your dark inner thighs take a half of lemon and squeeze the lemon juice out of the lemon and mix the lemon juice with about 3 tablespoons of coconut oil and mix it together.
Then apply the coconut oil and lemon juice mixture to your inner thighs and massage the mixture onto the dark inner thighs.
And then once your skin absorbs the lemon juice and coconut oil you can wash the area with lukewarm water.
Do the above regularly and within a week you should see lighter inner thighs.