Happy Gene is found in Worlds 4 through 6 in Magatsu Mandala within the Midnight Channel. It will try to afflict the party with status effects and its Galgalim Eyes skill can potentially reduce a party member's HP to 1 along with causing Enervation. After being defeated, it may drop Unthinkable Metal. Selling 4 Unthinkable Metal will unlock the Militia Dagger weapon for Yosuke Hanamura in the shop.
In Golden, Happy Gene has no offensive skills. It can erect both physical and magical barriers, sacrifice itself to heal an ally to full, or cure all ailments except for Down. It protects its weakness with Dodge Physical.