Like above anon said, just close analysis of the lines and how the voice acting delivered it, along with what canon said about their personal history and relates to other swords and/or Saniwa. Save for maybe a few swords, each character basically have their own recorded history + main characterisation gimmick.
After that is headcanon to fill in the blanks.
There's the anime (Hanamaru, plus ufotable anime next yea)r, plus the musicals & stage adaptation. So some characters would have more material to drawn from.
Re: CHARACTER ADVICE
Like above anon said, just close analysis of the lines and how the voice acting delivered it, along with what canon said about their personal history and relates to other swords and/or Saniwa. Save for maybe a few swords, each character basically have their own recorded history + main characterisation gimmick.
After that is headcanon to fill in the blanks.
There's the anime (Hanamaru, plus ufotable anime next yea)r, plus the musicals & stage adaptation. So some characters would have more material to drawn from.