It isn't nonsense... It is called being a psychopath. I mean he had no mother to educate him. Had a super strict uncle who beat him day and night as training which lead to his own death. Were you expecting him to grow with good morals?
no it's nonsense, there's no way you would continue a match when your opponent says they've kidnapped and murdered your mother, whether it's true or not.
"i'll beat you... in kendo!" shut up, no one acts this way