How many movies have Hideaki Hatta and Yukiko Horiguchi collaborated on?

They have worked on 3 movies together! Their first movie together was Munto 2: Beyond the Walls of Time (2005) while their highest rated movie together was K-On! The Movie (2011). They have not worked together since K-On! The Movie (2011). They are most known for their animation films together.

K-On! The Movie (2011)

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Executive Producer
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Character Designer
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Animation Director
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Key Animation
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Supervising Animation Director

The Disappearance of Haruhi Suzumiya (2010)

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Producer
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Animation Director
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Key Animation

Munto 2: Beyond the Walls of Time (2005)

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Executive Producer
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Key Animation