Shiranui led Chuck and company to a clearing and called Saisei out.  "Saisei, meet two of your descendants of sorts," he introduced, "Hibiki over there needs to learn how to properly handle her power."
"[i]I shall do what I can, but I cannot promise any favourable results,[/i]" the Mewtwo agreed, leaving a warning.  Saisei addressed Gileta and Hibiki.  "[i]Listen up, you two.  The first thing I'll teach you is why you go berserk so it will put into context how you can control it.  My genetic structure has a flaw that the humans failed to take into account when they created me and it took the efforts of Sherlock and Jean* researching epigenetics to find it.  The two Alakazam named this flaw the Berserk Gene.  It would appear to me that if the humans that created you spliced some of my genetic material with yours to increase your power to rival the legendary Pokémon, they may have inadvertently given you and all the others this flawed gene as well,[/i]" Saisei explained.

* Shiranui's Alakazam