Japanese by Example
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All that murder planning for nothing with 水の泡になる

Idiom Explanation: All that effort for nothing with 水の泡になる

名探偵コナン » Volume 5 » Page 83

After discovering who the murderer is, Conan explains why the murderer went after Ran. He pinpoints when Ran unknowingly discovered a vital clue.

コナン:
「あの時(とき)、蘭(らん)の事(こと)気(き)にもとめてなかったが、もし思(おも)い出(だ)されたらせっかく組(く)み立(た)てたこの殺人(さつじん)計画(けいかく)がすべて水(みず)の泡(あわ)になる…」
"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."