I'm terrible with regex, but this might get you somewhere. Replaces everything but lowercase alpha and underscores.
A = {'9.banana' 'orange-123_juice' 'ン戦国時' 'apple_sauce' 'abcクルミ' 'peach' 'pear' 'ピラミッド' 'cherry'}.'
B = regexprep(A,'[^a-z_]','')
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