I've been playing this game over and over again since it first came out on XBox (1998). Now I am enjoying this game on the PS4 (the old PC version) and on new game plus. I made sure that I bought the Ragna Rock when it first came available and upgraded my weapon to Enchanted Bluesteel at beginning of game. I just got to level 79 (haven't rescued Irina yet) and there it was.....Rush learned Cerulean Rain!!! When I first played the game (not on new game plus), for the life of me I could not get him to learn any special weapon arts. I swear, that Ragna Rock on new game plus ("bonus unknown") is leveling up EVERYTHING and EVERYONE quickly.