Ok, the controlling document would be the trust document itself. It would discuss the powers of the trustee and the process for any successor trustees.
For example from one I drafted:
TRUSTEE APPOINTMENTS: The Trustor, hereby appoints __________________, the Trustor, as Trustee of this Trust. If the Trustor, is unable to serve as Trustee for any reason, then the Trustor hereby appoints __________________ as Successor Trustee. If neither the first or second Trustee are able to serve as Trustee for any reason, then the Trustor hereby appoints __________________ as Successor Trustee, whether one or more. The Trustee shall have all powers as provided in this agreement and the laws of the State of Kentucky. The principal place of administration of this trust is the Trustors place of residence, regardless of the residence of the Trustee. If multiple or Co-Trustees are appointed their exercise of powers shall be governed by Kentucky Revised Statutes Title 33 Section 386.825. In the event a vacancy in the office of Trustee occurs and there is no successor trustee, the existing Trustee, if one, and the beneficiaries, or the beneficiaries, if there is no trustee, may agree to a non-judicial change in the trustee by amendment to this Trust agreement.
In the event that there was not similar language in the trust document, you would then have to look at Hawaii statutes to determine the Trust laws. Under the Hawaii Probate Code if the trustee (or co-trustee) is not acting in compliance with the terms of the trust or has a conflict that would make it impossible for him to complete his duties, the beneficiary or the other co-trustee can petition the probate court where the trust is registered to have him removed and replaced either by a successor trustee or an independent trustee appointed by the court.
§560:7-301 General duties not limited. Except as specifically provided, the general duty of the trustee to administer a trust expeditiously for the benefit of the beneficiaries is not altered by this chapter. [L 1976, c 200, pt of §1
§560:7-204 Court; concurrent jurisdiction of litigation involving trusts and third parties. The court of the judicial circuit in which the trust is required to be registered has concurrent jurisdiction with other courts of this State of actions and proceedings to determine the existence or nonexistence of trusts created other than by will, of actions by or against creditors or debtors of trusts, and of other actions and proceedings involving trustees and third parties. Venue is determined by the rules generally applicable to civil actions. [L 1976, c 200, pt of §1]