Argument Mutuality in contact zones has been emphasized in cross-cultural knowledge interaction in re-evaluating power dynamics between centers and peripheries and in showing the hybridity of modern science. This paper proposes an analytical pause on this attempt to better invalidate centers by paying serious attention to the limits of mutuality in transcultural knowledge interaction imposed by asymmetries of power. An unusually reciprocal interaction between a Japanese forester, Ishidoya Tsutomu (1891-1958), at the colonial forestry department, and his Korean subordinate Chung Tyaihyon (1883-1971) is chosen to highlight an inescapable asymmetry induced by the imperial power structure. Ishidoya, positioning himself as a settler expert, as opposed to a scientist in Tokyo, pursued localized knowledge in growing interaction with Chung, resulting in Ishidoya's career change as a herbalist focusing on traditional medicine and Chung's leadership in Korean-only botanizing. However, their mutual transformations, limited by asymmetric constraints on their choices, did not unsettle the imperial power structure or the centrality of centers.