HM Kokoro's Theme: The Lost Emotion

This is Hata no Kokoro's theme from Touhou 13.5: Hopeless Masquerade

Now, I'm genuinely impressed by this theme. It's powerful, intimidating, and almost terrifying. However, it belongs to an emotionless girl, who has lost her mind due to misplacing her Mask of Hope. It seems strange, that such a girl would possess such a theme with so much emotion.

I'm also interested by the rivalry between Koishi and Kokoro. Their situation seems to overlap, yet there is so much tension between the two.
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Image 1:
Artist: はね (tag: hane_(azelye))
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=21315987

Image 2:
Artist: 慎之介 (tag: white-aster)
http://www.pixiv.net/member_illust.php?mode=medium&illust_id=36523324