Metaplexis japonica
A specific plant species; the Japanese name かがみいも refers to Metaplexis japonica. Cross-referenced with 蘿芋, which may be a synonym or related name. This is a botanical term, not common in everyday conversation.
See also: ガガイモ
Metaplexis japonica is a climbing plant distributed in Japan and China.
I saw a photo of a Metaplexis japonica flower in a field guide.