If I want to write for example "Mr. K". I don't want to use just a single letter. Should I write it like "Mr. Kei", "Mr. Kay" or "Mr. Key"?
Update:
Let us imagine there was somebody with name Mr. King given at birth. He doesn't like his surname, but he likes when others address him as "Mr. K". So, he wants to change his surname. But he doesn't want to use just a single letter - it is too short. So is "Mr. Kay" the right way for his purpose?