Koichi-sama can't stand it if everything isn't exactly the way he wants.
It would be rude if you don't attach the formal name ender, sama, to the recipient's name when you send letters in Japan.
Mr. Koichi from Tofugu, party of nine. Your table is ready.
Add this onto the end of someone's name. It's probably too polite, to be honest, unless you're talking to one of your customers or something. It's good to know, but you're probably not going to use it much, despite seeing and hearing it fairly often.
The reading is the same as what you learned with the kanji.