http://en.touhouwiki.net/wiki/Organic_Compound#The_Woman_Called_Kazami_Yuuka_.282013-08-12.29 The Woman Called Kazami Yuuka (2013-08-12) Translated by pesu, edited by Ean
Think of it this way: she just has to wait a half a century or so for Marisa to die and then pick up Rinnosuke on the grief rebound. Youkai lifespans, eh?