Factions

KimetsuCraft assigns every entity to one of three factions. Your faction determines who you can hit and who attacks you on sight. Once you learn a breathing style and reach level 1, you're a Slayer -- there's no manual selection, the game assigns it based on what you are.

Faction	Who Belongs
SLAYER	Slayer NPCs and any player with a breathing style (level > 0)
DEMON	All demon entities
OTHER	Vanilla mobs, animals, and any unaligned entity

Damage Rules

Slayers can always damage Demons, and Demons can always damage Slayers. This is hardcoded.

Player-to-player damage is always active and cannot be disabled through the mod. If another player hits you, it connects -- regardless of faction.

Friendly fire in KimetsuCraft refers specifically to damage between players and Slayer NPCs. By default, this is enabled -- a Slayer player and a Slayer NPC can hurt each other. This can be toggled in the mod config for a more cooperative experience.

Alliance Checks

The faction system respects the vanilla Minecraft alliance system. If two entities are allied through vanilla mechanics (such as tamed wolves belonging to the same player), the faction system won't override that relationship.

Entities in the OTHER faction interact with Slayers and Demons through normal vanilla aggro rules.