this structure is already hardcoded

if you use same attribute (e.g. :contains for parent-child relationship all the way down, then you can write a generic recursive query)

although recursive query will find everything on its path, not just leaves

(d/q '[:find ?c
       :in $ % ?p
       :where (contains ?p ?c)]
  db
  [[(contains ?p ?c)
    [?p :contains ?c]]
   [(contains ?p ?c)
    [?p :contains ?x]
    (contains ?x ?c)]]
  (d/entid db [:name "asia"]))