宗主 is read as そうしゅ (soushu) and means suzerain.
そうしゅ
soushu
そうしゅこく
suzerain state
そうしゅけん
suzerainty
はんしゅうきょうしゅぎ
opposition to religion
ひしゅうきょうしゅぎ
secularism
そうけ
head of family
しゅうきょう
religious activity
しゅうそ
sect founder
しゅう
tenets (of a religious sect)
しゅうは
school (e.g. of poetry)
しゅうもん
(religious) denomination
むね
instructions
しゅうきょうか
religious leader