館主 is read as かんしゅ (kanshu) and means manager.
かんしゅ
kanshu
かんちょう
superintendent
かんいん
personnel (of public building)
やぬし
landlord
じしゅ
independence
もちぬし
owner
じぬし
landowner
あるじ
entertaining someone as one's guest
おも
main secondary or supporting role (in kyogen)
しゅ
(one's) master
しゅう
ぬし
husband
てんしゅ
shopkeeper