This is Eirin Yagokoro's theme from Touhou 8: Imperishable Night
Eirin's theme is still so powerful, even after such a long time. The piano sounds like someone retelling an old folk story, while the trumpets are the story unfolding in it's own present. Eirin is possibly the oldest and most wise in all of Gensokyo, and this theme certainly lets you know that. She really is like the Eternal Omoikane.
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Artist: なむこ (tag: namuko)
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=22409619
Home » プレイリスト » Youtube » IN Eirin's Theme: Gensokyo Millenium ~ History of the Moon (Re-Extended)