Tourism is a type of Travel. Travel is related to Case. 
Unlikely is a synonym of Unlike. Unlike is related to Different. Different is a different concept from Usual. Usual is a synonym of Simple. 
Tourism --IsA--> Travel <--RelatedTo--> Case 
Unlikely <--Synonym--> Unlike <--RelatedTo--> Different <--DistinctFrom--> Usual <--Synonym--> Simple 