Christopher

"Jujutsu kaisen - 0" ( The original 4 chapter long One-Shot manga that was originally titled "Tokyo Metropolitan Curse Technical School" before being reworked into "JJK-0") serves as a prequel to vanilla "Jujutsu Kaisen" that we know and love. So technically this new manga is going to be JJK-3, as JJK-0 would be the first, "vanilla" JJK would be the second, and the new manga, JJK-Mojuro, will be the third entry into the series