布洛妮婭，你也有份嗎？

Can be done in Simulated Universe 6 or Forgotten Hall 15. You have a fraction of a second to reset the game and retry the battle if some other unit defeats Cocolia. Unfortunately you need to own Bronya to get this achievement.

"Et tu, Bronya?" is a phrase that alludes to the famous line "Et tu, Brute?" from William Shakespeare's play The Tragedy of Julius Caesar. In the original line, Julius Caesar utters these words in disbelief and disappointment upon realizing that his trusted friend Brutus is also involved in the plot to assassinate him. By adapting the phrase, it suggests a similar sentiment of betrayal or shock directed towards Bronya by her mother.