 It is called Kadupul flower in Sri Lanka (Sri Lanka’s native blossom)

The Chinese chengyu (four character idiom) 曇花一現 (tán huā yī xiàn) use this flower (tan-hua; 曇花) to describe someone who has an impressive but very brief moment of glory, like a "flash in a pan," since an "Epiphyllum oxypetalum" plant might bloom only once a year over a few days.Therefore, someone described as "曇花一現" is generally understood to be a person who shows off or unexpectedly gains some achievement and is thought to be an exception or only lucky.The flower also has a rich history in Japan, where it is known as the (Gekka Bijin) or "Beauty under the Moon".