Future is the opposite of Actual. Actual is the opposite of Theoretical. 
Could is related to Have. Have is the opposite of Desire. Desire is related to Sexual. Sexuality is derived from Sexual. 
Future <--Antonym--> Actual <--Antonym--> Theoretical 
Could <--RelatedTo--> Have <--Antonym--> Desire <--RelatedTo--> Sexual <--DerivedFrom-- Sexuality 