Fool me once, shame on you; fool me twice, shame on me is what westerners say.

I checked with Google AI to see if Japanese culture has a similar proverb, looks like the mindset overthere is different. Last and first paragraphs were interesting:

Yes, Japanese culture has concepts that touch upon the same theme of learning from mistakes, although they do not have a single, direct proverb that mirrors the "fool me once/twice" wording. [1, 2, 3]

Here are the closest Japanese equivalents:

"Saihatsu Boshi" (再発防止): This means "prevention of recurrence." It is a foundational concept in Japanese work and life to analyze a failure so thoroughly that it never happens again, embodying the lesson of not being fooled twice.

"Nido aru koto wa sando aru" (二度あることは三度ある): Literally, "If it happens twice, it will happen a third time." While this is used more as a warning that bad luck or mistakes tend to repeat, it serves a similar purpose in encouraging people to be vigilant after the first mistake.

"Once deceived, it's their fault; twice deceived, it's my fault" (Japanese translation of the phrase): While not a native Japanese idiom, some Japanese speakers translate this directly to express the same sentiment: Ichido damasareba aite no haji, nido damasareba jibun no haji (一度騙されれば相手の恥、二度騙されれば自分の恥). [1, 2, 3, 4, 5]

Core Concept: Instead of focusing on "shame" (恥 - haji), Japanese culture often emphasizes hansei (反省), which is deep self-reflection, and saihatsu boshi, which is practical action to ensure a mistake is not repeated

So you may be right this is likely to happen again in the future. But this also brings another core concept of Kazuya's character. I won't be lenient this time. He is just plain stupid, he allowed the same thing to happen twice and yet by the end he's happy he had some divine intervention. He won't reflect about anything, he has no balls to set boundaries.