The expression 水の泡(になる (also 水の泡となる) is used to describe something that has been wasted, lost, or ruined, much like how bubbles quickly dissipate and disappear. The phrase conveys the idea of efforts, work, or plans that come to nothing or are in vain. Similar expressions in English include “go up in flames”, “go up in smoke”, “go down the drain”, and “gone to waste”.
Literal Meaning
This expression literally translates as “to become bubbles of water”.
Usage
It might be used when something that was expected to succeed or had potential ends up being fruitless or completely undone. The nuance is generally one of disappointment or frustration, emphasizing the futility or the sudden disappearance of something that was once tangible.
“Ran didn't think anything of it at the time, but if she remembered it, all the murderous plans he worked so hard on putting together would go up in smoke.”
Literal: “At the time, Ran didn't pay it any mind, but if she remembered, this murder plan he had gone to the trouble of assembling would all become bubbles of water...”
Although Fujimiya loses her memory of friends every Monday morning, she and Hase have become close enough that she feels comfortable around him when meeting him “for the first time” at school each Monday. Hase fears that progress will be lost during summer break.
長谷(:
「俺(はせっかくの今(までの努力(が水(の泡(になるのが嫌(なの!」
“I hate seeing all my hard work up to now go down the drain!”
Literal: “I hate my hard work up to now becoming bubbles of water!”