Gate is related to Open. Open is a synonym of Appear. Appear is the opposite of Disappear. Disappear is a synonym of Go. 
Companion is related to Pet. Pet is a synonym of Sister. 
Gate <--RelatedTo--> Open <--Synonym--> Appear <--Antonym--> Disappear <--Synonym--> Go 
Companion <--RelatedTo--> Pet <--Synonym--> Sister 