Gaku, having satisfied Kai by discovering the hidden secret in Ranna's cooking, unexpectedly meets his childhood friend and Math Olympiad rival Kagura Musashi. Kagura looks at Gaku coldly, due to him having given up on the path to becoming a mathematician, and he ends up creating one of his "mathematical mind" meals for her. However, his attempt to surpass the "umami synergy" as shown by Ranna fails miserably, when he was so sure it would work. Gaku finds a solution to his problem laying in the memories he has with his father.

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