Displaced Orphan Reimu was a Lonely Wanderer... seemingly All Alone in the World, until she Came upon a Shinto Shrine Ground

and Met Momiji "Maple" Hakurei; a Fox-Miko Lady that is the Well-Regarded Sole Caretaker of the Aging Yoshinaga Shrine.

Naturally, Maple's Big-Hearted Nature being what it is; She took Reimu in to Live at the Shrine for as Long as she wants to.

Eventually, Reimu's Uncertain, Standoffishness Fades Away... and the Two Grow so Close that Maple Adopts Reimu as her Sister♥

and the Two Become Well-Known and Beloved by the Nearby Village Community

as the ♥Hakurei Sisters♥ of the Rebuilt and Rechristened ♥Hakurei Shrine♥