GreatWesternBank.com Filed by Great Western Bancorp, Inc. Commission File No. 001-36688 Filed Pursuant to Rule 425 Under the Securities Act of 1933 and Deemed Filed Pursuant to Rule 14a-12 Under the Securities Exchange Act of 1934 Subject Company: HF Financial Corp. Commission File No. 033-44383 Date: December 9, 2015

GreatWesternBank.com

GreatWesternBank.com

GreatWesternBank.com

GreatWesternBank.com

GreatWesternBank.com No Offer or Solicitation This communication is not a solicitation of a proxy from any stockholder of HF Financial Corp. This communication is for informational purposes only and is neither an offer to purchase, nor a solicitation of an offer to sell, any securities in any jurisdiction pursuant to the proposed transaction or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of any applicable law. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933. Important Additional Information and Where to Find It In connection with the Agreement and Plan of Merger by and between Great Western Bancorp, Inc. (“Great Western”) and HF Financial Corp., Great Western will file with the Securities and Exchange Commission (“SEC”) a Registration Statement on Form S-4 that will contain a proxy statement of HF Financial Corp. and a prospectus of Great Western, as well as other relevant documents concerning the proposed transaction. STOCKHOLDERS OF HF FINANCIAL CORP. ARE URGED TO READ THE REGISTRATION STATEMENT AND THE PROXY STATEMENT/PROSPECTUS REGARDING THE PROPOSED TRANSACTION WHEN IT BECOMES AVAILABLE AND ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THOSE DOCUMENTS, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT GREAT WESTERN, HF FINANCIAL CORP. AND THE PROPOSED TRANSACTION. The Registration Statement, including the proxy statement/prospectus, and other relevant materials (when they become available), and any other documents filed by Great Western and HF Financial Corp. with the SEC, may be obtained free of charge at the SEC’s website at www.sec.gov. Documents filed by Great Western with the SEC, including the Registration Statement, may also be obtained free of charge from Great Western’s website (www.greatwesternbank.com) under the “Investor Relations” heading and the “SEC Filings” sub-heading, or by directing a request to Great Western’s Investor Relations contact, David Hinderaker at David.Hinderaker@greatwesternbank.com. Documents filed by HF Financial Corp. with the SEC may also be obtained free of charge from HF Financial Corp’s website (www.homefederal.com under the “Investor Relations” heading and the “SEC Filings” sub-heading, or by directing a request to HF Financial Corp’s Investor Relations contact, Pamela F. Russo at prusso@homefederal.com. Participants in the Solicitation Great Western, HF Financial Corp., and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from the stockholders of HF Financial Corp., in connection with the proposed merger transaction. Information about the directors and executive officers of Great Western is available in Great Western’s definitive proxy statement for its 2015 annual meeting of stockholders as previously filed with the SEC on January 5, 2015, and other documents subsequently filed by Great Western with the SEC. Information about the directors and executive officers of HF Financial Corp., is available in HF Financial Corp.’s, definitive proxy statement, for its 2015 annual meeting of stockholders as previously filed with the SEC on October 16, 2015. Other information regarding the participants and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the Registration Statement and including the proxy statement/prospectus, and other relevant documents regarding the transaction filed with the SEC when they become available. Forward-Looking Statements This document contains forward-looking statements. You can generally identify forward-looking statements by the use of forward-looking terminology such as “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “explore,” “evaluate,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “seek,” “should,” or “will,” or the negative thereof or other variations thereon or comparable terminology. These forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond GWB’s and HF Financial Corp’s control. Statements in this document regarding Great Western, HF Financial Corp. and the proposed merger that are forward- looking, including projections as to the anticipated benefits of the proposed transaction, the impact of the proposed transaction on anticipated financial results, the synergies from the proposed transaction, and the closing date for the proposed transaction, are based on management’s estimates, assumptions and projections, and are subject to significant uncertainties and other factors, many of which are beyond the control of Great Western and HF Financial Corp. In particular, projected financial information for the combined company is based on management’s estimates, assumptions and projections and has not been prepared in conformance with the applicable accounting requirements of Regulation S- X relating to pro forma financial information, and the required pro forma adjustments have not been applied and are not reflected therein. None of this information should be considered in isolation from, or as a substitute for, the historical financial statements of Great Western or HF Financial Corp. Important risk factors could cause actual future results and other future events to differ materially from those currently estimated by management, including, but not limited to: the

GreatWesternBank.com timing to consummate the proposed transaction; the risk that a condition to closing of the proposed transaction may not be satisfied and the transaction may not close; the risk that a regulatory approval that may be required for the proposed transaction is delayed, is not obtained or is obtained subject to conditions that are not anticipated; the combined company’s ability to achieve the synergies and value creation contemplated by the proposed transaction; management’s ability to promptly and effectively integrate the businesses of the two companies; the diversion of management time on transaction-related issues; change in national and regional economic conditions; the effects of governmental regulation of the financial services industry; industry consolidation; technological developments and major world news events. For more discussion of important risk factors that may materially affect Great Western and HF Financial Corp., please see the risk factors contained in Great Western’s Annual Report on Form 10-K for its fiscal year ended September 30, 2014 and HF Financial Corp’s Annual Report on Form 10-K for its fiscal year ended June 30, 2015, both of which are on file with the SEC and available through the SEC’s website at www.sec.gov. You should also read Great Western’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2015, which is on file with the SEC. No assurances can be given that any of the events anticipated by the forward-looking statements will transpire or occur, or if any of them do occur, what impact they will have on the results of operations, financial condition or cash flows of Great Western, HF Financial Corp. or the combined company. None of Great Western nor HF Financial Corp. assumes any duty to update or revise forward-looking statements, whether as a result of new information, future events or otherwise, as of any future date.