nihongotojapan.com/en/grammar/grammar-keigo-guide
Complete guide to Japanese honorific language explaining the three types of keigo, their rules and formulas, with business examples for phone calls, emails, and client visits.
GrammarBusiness and keigoKeigo and politenessBusiness JapaneseJLPT N3JLPTTutors and teachersConditionalsSentence patternsQuizzes