HR 5 is the highest rank in the game. It is a tough rank to get, but is worth it. You must complete 4 of the quests in HR 4. They are THE SHADOW IN THE CAVE, THE BASARIOS:INVISIBLE TERROR, TWO ROCK WYVERNS, and THE LAND AND THE SKY. You will then get the urgent quest which is PINK AND AZURE. Complete it and you will become HR 5.