If I'm not mistaken, these are the kanji used: あっぷぷ!
These translate to "Pu pu there!" (Grammar is reversed). Generally the sound effect "pu pu (pu pu pu)" is beeping though, like a telephone. But in this context it might be a sort of "peekaboo".
I am not Japanese, nor can I read it, I just "internetted a bit". So if there is anybody who can back this up/correct it, please feel free to! :)
These translate to "Pu pu there!" (Grammar is reversed). Generally the sound effect "pu pu (pu pu pu)" is beeping though, like a telephone. But in this context it might be a sort of "peekaboo".
I am not Japanese, nor can I read it, I just "internetted a bit". So if there is anybody who can back this up/correct it, please feel free to! :)