increase_house_relation_level_effect

increase_house_relation_level_effect = {
	save_scope_as = house
	$HOUSE$ ?= { save_scope_as = other_house }
	if = {
		limit = {
			exists = scope:house
			exists = scope:other_house
			scope:house != scope:other_house
		}
		if = {
			limit = { has_house_relation_with = scope:other_house }
			random_house_relation = {
				limit = {
					any_relation_house = { scope:other_house = this }
				}
				save_scope_as = house_relation
				if = {
					limit = { has_house_relation_level = feud }
					scope:house = {
						set_house_relation_level_effect = {
							HOUSE = scope:other_house
							REASON = $REASON$
							LEVEL = rivalry
						}
					}
				}
				else_if = {
					limit = { has_house_relation_level = rivalry }
					scope:house = {
						set_house_relation_level_effect = {
							HOUSE = scope:other_house
							REASON = $REASON$
							LEVEL = quarrel
						}
					}
				}
				else_if = {
					limit = { has_house_relation_level = quarrel }
					scope:house = {
						set_house_relation_level_effect = {
							HOUSE = scope:other_house
							REASON = $REASON$
							LEVEL = neutral
						}
					}
				}
				else_if = {
					limit = { has_house_relation_level = neutral }
					scope:house = {
						set_house_relation_level_effect = {
							HOUSE = scope:other_house
							REASON = $REASON$
							LEVEL = cordial
						}
					}
				}
				else_if = {
					limit = { has_house_relation_level = cordial }
					scope:house = {
						set_house_relation_level_effect = {
							HOUSE = scope:other_house
							REASON = $REASON$
							LEVEL = friendly
						}
					}
				}
				else_if = {
					limit = { has_house_relation_level = friendly }
					scope:house = {
						set_house_relation_level_effect = {
							HOUSE = scope:other_house
							REASON = $REASON$
							LEVEL = amity
						}
					}
				}
			}
		}
		else = {
			set_house_relation_level_effect = {
				HOUSE = scope:other_house
				REASON = $REASON$
				LEVEL = cordial
			}
			random_house_relation = {
				limit = { any_relation_house = { this = scope:other_house } }
				save_scope_as = house_relation
			}
		}
	}
}

As written in game/common/scripted_effects/10_dlc_tgp_house_relation_scripted_effects.txt.