Convergent development can lead different navies toward similar answers when wartime pressures pose the same problem. Britain's light fleet carriers grew from studies behind HMS Unicorn, an aviation-support ship intended to sustain treaty-limited fleet carriers. Wartime adaptation turned that support lineage into an economical light-carrier design that could also return to aviation-support work. Japan's Unryu and Ikoma families emerged on essentially the same design and construction timeline through a separate Japanese lineage. Their visual similarity therefore does not show that one navy copied the other.
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The Unryu class was not a British copy
Parallel Japanese and British light-carrier programs illustrate how similar wartime pressures can produce similar ships without direct copying.