Even while Dabura was still the Supreme King of the Demon Realm, Arinsu was scheming to conquer her home dimension. During the events of Dragon Ball Z, Arinsu arrived on Earth. Staying in the shadows shortly after Babidi used Majin Vegeta’s energy to awaken Majin Buu. Avoiding the attention of the Z-Warriors, Arinsu bided her time until Vegeta fought Buu. When Vegeta blew himself up with his Final Explosion, he blew Buu away as well. Although Buu was ultimately unharmed by the attack, it did split his essence into thousands of tiny pieces.
When no one was watching, Arinsu collected one of the pieces of Buu’s essence for her own purposes. Buu’s pieces would soon serve as the key ingredient in the spell she was preparing to take over the Demon Realm, making Vegeta once again directly responsible for enabling the machinations of a main antagonist. Arinsu wouldn’t have been able to advance her plan without him. That said, as confident as Arinsu was in herself and her plan, she knew that something could go wrong, and that the Z-Warriors could eventually pose a threat to her – leading her to formulate a back-up plan.