Illyasviel von Einzbern

[Illyasviel von Einzbern from Fate/Stay Night] A member of the Einzbern family, a homonculus modified with the goal of becoming the Holy Grail of the Fifth Holy Grail War and the Master of Berserker. An outgoing and optimistic girl who tends to get into mischief but can also be callous and ruthless towards those she considers enemies.

(Note: The reason for her appearance is because she was modified to such an extent that it caused her growth to slow down abnormally.)