DESCRIPTION:
A theme of Sengo Sanada, the Extra Stage boss. It has been composed by Misora.

Merry X-Stage and a Happy PTSD Samurai. Now without all that Legendary Hero mode challenge killer and such.
(...I barely got past her second spellcard ;-;)

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The soundtrack comes from "Book of Star Mythology", a fanmade Touhou script available for free, featuring soundtracks of multiple composers.

You can read more about the project here: https://en.touhouwiki.net/wiki/Book_of_Star_Mythology
You can also find download links there.

The soundtrack has been extended to play for 30 minutes.