I'm reading a manga where two girls are fighting in public while others are standing around making bets on who will win (I should also note the crowd is crudely referring to the women as 無乳 and 巨乳).

One of the onlookers says: 賭けになってねーじゃねえか。無乳が最後にうっかりを発動させるにエリクサー10 個

I'm confused by the meaning of うっかりを発動させる. I can only guess that maybe the onlooker is betting 10 elixirs that the 無乳 girl will make the other girl invoke the "うっかり" excuse and forfeit the match? What does that even mean?

Any help would be greatly appreciated!


1 Answer 1


うっかり itself is something like "absentmindedness", "carelessness" or "oversight", and it is jokingly treated as 無乳's "(bad) skill" or "(negative) trait". 発動させる in this context is the same as 発動する ("to trigger/invoke/activate"). 発動する works both as a transitive verb ("to trigger X") and an intransitive verb ("X takes effect"). See:

Therefore, 無乳がうっかりを発動させる means that the 無乳 herself will make a terrible mistake, not that 無乳 will cause the other girl to make a mistake. This is a comical phrase unique to RPG-themed or so-called isekai fantasy, but it can be used in everyday conversations among otaku who like such genres.


(I'll bet) 10 Elixirs that the flat one will (accidentally) activate Carelessness (and lose) in the end.

Things like うっかり or 天然ボケ are often treated as "moe traits". I get the impression that this 無乳 girl may be a character who always fails in the end but gains popularity all the more for her carelessness.

  • Thanks for your response! Can this expression be used with any quality, trait, or adjective?
    – skywalker
    Commented Apr 14 at 5:38
  • @skywalker うっかりを発動させる is already a comical phrase. You shouldn't say something like this unless you really know what you are doing.
    – naruto
    Commented Apr 14 at 6:39

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .