translated most of it but can't make out what the string of characters on the speech bubble border is

ngo_enthusiast said:

translated most of it but can't make out what the string of characters on the speech bubble border is

キャハハッ

Moonspeaker said:

キャハハッ

I also tweaked the "apology" a bit. Given the speaker is laughing, it doesn't sound very sincere.