Need someone can speak or write Japanese help me. Or someone can know english sfx.
I have a picture ( manga ) :

That in a first picture. The sfx mean : boof <= i can't search in dictionary.
But look like : だ
I search it and get the mean : " I " is Vietnamese mean : Tôi
It's not logical.
Someone can tell me what is mean. i'm sorry for my bad english.