This is a rather interesting one, especially considering that Shoutoku Taishi supposedly did appear in the dream of Buddhists as a representation of Kannon and told them marriage was alright. Smooth preparations, Miko, really smooth... I kinda love the idea that these two have a backstory before Gensokyo, even if it isn't the case. Not the only one like that either, there's also one where Miko was responsible for Shou becoming a youkai.