This article is for Kakyoin as an enemy, for Kakyoin's stats as an ally, check his stand's page Hierophant Green.
For Kakyoin's role in the Anime/Manga, you might want to check "Noriaki Kakyoin" in JJBA's wiki.
Noriaki Kakyoin is an original character from the Anime and Manga series "Jojo's Bizarre Adventure", and the first major boss to be encountered in "Jojo's Bizarre Adventure: The Seventh Stand User", being also the first one to actively use a Stand.
A Japanese student hired by DIO, Kakyoin is the first assassin commanded by him to fight the Joestars. In order to do so, he assaults both you and Jotaro inside of your school in Japan, possessing a nurse with his Long Range/Control stand "Hierophant Green".
Its after this battle that you join the Joestar Group. Marking the first step in your journey with them.
After being defeated and having his (DIO's) flesh bud removed, Kakyoin also becomes a major ally of the Joestars.
Attack Pattern and StrategyEdit
Kakyoin is really strong compared to the normal enemies you can find in Japan (Those being, delinquents and murdedolls), but having Jotaro in your party certainly helps balancing things out.
In the first stage, (When you fight as Jotaro against the Nurse) the only way to win is to keep your guard up until you can pull H.G out of her mouth. This will normally happen in two or three turns.
In the second one (Which is, Jotaro and the player against Kakyoin himself), he will use two powerful attacks to lower your health: Hierophant barrier (Which damages both characters) and Emerald Splash (Which damages only one). The strategy here is just to spam Star Platinum's "Ora Ora" attack and use your own stand for either attack or support until the battle ends. The preparations you should take before this battle are simply to level up a bit before jumping into it, and being confident of both your's and your character's skills in combat.