PROMISSORY NOTE DATED APRIL 24, 2026, ISSUED TO FDB IV

Exhibit 10.6

THIS PROMISSORY NOTE (THIS “NOTE”) HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”). THIS NOTE HAS BEEN ACQUIRED FOR INVESTMENT ONLY AND MAY NOT BE SOLD, TRANSFERRED OR ASSIGNED IN THE ABSENCE OF REGISTRATION OF THE RESALE THEREOF UNDER THE SECURITIES ACT OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY IN FORM, SCOPE AND SUBSTANCE TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.

PROMISSORY NOTE

FOR VALUE RECEIVED and subject to the terms and conditions set forth herein, Norient Acquisition, a Cayman Islands exempted company (“Maker”), promises to pay to FDB IV (“Payee”), or order, the principal sum of up to Three Hundred Fifty Thousand U.S. Dollars (U.S.$350,000) or such lesser amount as shall have been advanced by Payee to Maker and shall remain unpaid under this Note on the Maturity Date (as defined below) in lawful money of the United States of America, on the terms and conditions described below. All payments on this Note shall be made by check or wire transfer of immediately available funds or as otherwise determined by Maker to such account as Payee may from time to time designate by written notice in accordance with the provisions of this Note.

1. Principal. The entire unpaid principal balance of this Note shall be due and payable in full on the earlier of (i) the closing of the initial public offering of the Maker or (ii) December 31, 2026 (the “Maturity Date”), unless accelerated upon the occurrence of an Event of Default (as defined below). The principal balance may be prepaid at any time by Maker, at its election and without penalty. Under no circumstances shall any individual, including but not limited to any officer, director, employee or shareholder of Maker, be obligated personally for any obligations or liabilities of Maker hereunder.

2. Interest. No interest shall accrue on the unpaid principal balance of this Note.

3. Application of Payments. All payments shall be applied first to payment in full of any costs incurred in the collection of any sum due under this Note, including (without limitation) reasonable attorney’s fees, then to the payment in full of any late charges and finally to the reduction of the unpaid principal balance of this Note.

4. Events of Default. The following shall constitute an event of default (“Event of Default”):

(a) Failure to Make Required Payments. Failure by Maker to pay the principal amount due pursuant to this Note on the Maturity Date.

(b) Voluntary Bankruptcy, Etc. The commencement by Maker of a voluntary case under any applicable bankruptcy, insolvency, reorganization, rehabilitation or other similar law, or the consent by it to the appointment of or taking possession by a receiver, liquidator, assignee, trustee, custodian, sequestrator (or other similar official) of Maker or for any substantial part of its property, or the making by it of any assignment for the benefit of creditors, or the failure of Maker generally to pay its debts as such debts become due, or the taking of corporate action by Maker in furtherance of any of the foregoing.

(c) Involuntary Bankruptcy, Etc. The entry of a decree or order for relief by a court having jurisdiction in the premises in respect of Maker in an involuntary case under any applicable bankruptcy, insolvency or other similar law, or appointing a receiver, liquidator, assignee, custodian, trustee, sequestrator (or similar official) of Maker or for any substantial part of its property, or ordering the winding-up or liquidation of its affairs, and the continuance of any such decree or order unstayed and in effect for a period of sixty (60) consecutive days.

Remedies.

(a) Upon the occurrence of an Event of Default specified in Section 4(a) hereof, Payee may, by written notice to Maker, declare this Note to be due immediately and payable, whereupon the unpaid principal amount of this Note, and all other amounts payable thereunder, shall become immediately due and payable without presentment, demand, protest or other notice of any kind, all of which are hereby expressly waived, anything contained herein or in the documents evidencing the same to the contrary notwithstanding.

(b) Upon the occurrence of an Event of Default specified in Sections 4(b) or 4(c), the unpaid principal balance of this Note, and all other sums payable with regard to this Note, shall automatically and immediately become due and payable, in all cases without any action on the part of Payee.

6. Waivers. Maker and all endorsers and guarantors of, and sureties for, this Note waive presentment for payment, demand, notice of dishonor, protest, and notice of protest with regard to the Note, all errors, defects and imperfections in any proceedings instituted by Payee under the terms of this Note, and all benefits that might accrue to Maker by virtue of any present or future laws exempting any property, real or personal, or any part of the proceeds arising from any sale of any such property, from attachment, levy or sale under execution, or providing for any stay of execution, exemption from civil process, or extension of time for payment; and Maker agrees that any real estate that may be levied upon pursuant to a judgment obtained by virtue hereof, on any writ of execution issued hereon, may be sold upon any such writ in whole or in part in any order desired by Payee.

7. Unconditional Liability. Maker hereby waives all notices in connection with the delivery, acceptance, performance, default, or enforcement of the payment of this Note, and agrees that its liability shall be unconditional, without regard to the liability of any other party, and shall not be affected in any manner by any indulgence, extension of time, renewal, waiver or modification granted or consented to by Payee, and consents to any and all extensions of time, renewals, waivers, or modifications that may be granted by Payee with respect to the payment or other provisions of this Note, and agrees that additional makers, endorsers, guarantors, or sureties may become parties hereto without notice to Maker or affecting Maker’s liability hereunder.

8. Notices. All notices, statements or other documents which are required or contemplated by this Note shall be: (i) in writing and delivered personally or sent by first class registered or certified mail, overnight courier service to the address designated in writing, (ii) by facsimile to the number most recently provided to such party or such other address or fax number as may be designated in writing by such party or (iii) by electronic mail (including .pdf), to the electronic mail address most recently provided to such party or such other electronic mail address as may be designated in writing by such party. Any notice or other communication so transmitted shall be deemed to have been given on the day of delivery, if delivered personally, on the business day following receipt of written confirmation, if sent by facsimile or electronic mail, one (1) business day after delivery to an overnight courier service or five (5) days after mailing if sent by mail.

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9. Construction and Governing Law. THIS NOTE SHALL BE GOVERNED BY, AND CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO CONFLICTS OF LAW PRINCIPLES.

10. Severability. Any provision contained in this Note which is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction.

11. Amendment; Waiver. Any amendment hereto or waiver of any provision hereof may be made with, and only with, the written consent of Maker and Payee.

12. Trust Waiver. Notwithstanding anything herein to the contrary, the Payee hereby waives any and all right, title, interest or claim of any kind (“Claim”) in or to any distribution of or from the trust account to be established in which the proceeds of the initial public offering (“IPO”) to be conducted by the Maker (including the deferred underwriters discounts and commissions) and the proceeds of the sale of the private placement units to be issued in a private placement to occur prior to the closing of the IPO are to be deposited, as described in greater detail in the registration statement and prospectus to be filed with the Securities and Exchange Commission in connection with the IPO, and hereby agrees not to seek recourse, reimbursement, payment or satisfaction for any Claim against the trust account for any reason whatsoever.

13. Assignment. No assignment or transfer of this Note or any rights or obligations hereunder may be made by any party hereto (by operation of law or otherwise) without the prior written consent of the other party hereto and any attempted assignment without the required consent shall be void.

14. Successors and Assigns. This Note shall be binding upon and inure to the benefit of the parties hereto and their respective permitted successors and assigns, and no other person will have any right or obligation hereunder. Nothing in this Note shall be construed to create any rights or obligations except among the parties hereto, and no person or entity shall be regarded as a third-party beneficiary of this Note.

15. Severability. In the event that any court of competent jurisdiction shall determine that any provision, or any portion thereof, contained in this Note shall be unreasonable or unenforceable in any respect, then such provision shall be deemed limited to the extent that such court deems it reasonable and enforceable, and as so limited shall remain in full force and effect. In the event that such court shall deem any such provision, or portion thereof, wholly unenforceable, the remaining provisions of this Note shall nevertheless remain in full force and effect.

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16. No Waiver of Rights, Powers and Remedies. No failure or delay by a party hereto in exercising any right, power or remedy under this Note, and no course of dealing between the parties hereto, shall operate as a waiver of any such right, power or remedy of such party. No single or partial exercise of any right, power or remedy under this Note by a party hereto, nor any abandonment or discontinuance of steps to enforce any such right, power or remedy, shall preclude such party from any other or further exercise thereof or the exercise of any other right, power or remedy hereunder. The election of any remedy by a party hereto shall not constitute a waiver of the right of such party to pursue other available remedies. No notice to or demand on a party not expressly required under this Note shall entitle the party receiving such notice or demand to any other or further notice or demand in similar or other circumstances or constitute a waiver of the rights of the party giving such notice or demand to any other or further action in any circumstances without such notice or demand.

17. Waivers and Consents. The terms and provisions of this Note may be waived, or consent for the departure therefrom granted, only by a written document executed by the party entitled to the benefits of such terms or provisions. No such waiver or consent shall be deemed to be or shall constitute a waiver or consent with respect to any other terms or provisions of this Note, whether or not similar. Each such waiver or consent shall be effective only in the specific instance and for the purpose for which it was given, and shall not constitute a continuing waiver or consent.

18. Entire Agreement. This Note embodies the entire agreement and understanding between Payee and Maker with respect to the subject matter hereof and supersedes all prior oral or written agreements and understandings relating to the subject matter hereof. No statement, representation, warranty, covenant or agreement of any kind not expressly set forth in this Note shall affect, or be used to interpret, change or restrict, the express terms and provisions of this Note.

19. Headings and Captions. The headings and captions of the various subdivisions of this Note are for convenience of reference only and shall in no way modify or affect the meaning or construction of any of the terms or provisions hereof.

20. Counterparts. This Note may be executed in one or more counterparts, all of which when taken together shall be considered one and the same agreement and shall become effective when counterparts have been signed by each party and delivered to the other party, it being understood that both parties need not sign the same counterpart. In the event that any signature is delivered by facsimile transmission or any other form of electronic delivery, such signature shall create a valid and binding obligation of the party executing (or on whose behalf such signature is executed) with the same force and effect as if such signature page were an original thereof.

21. Construction. The parties hereto have participated jointly in the negotiation and drafting of this Note. If an ambiguity or question of intent or interpretation arises, this Note will be construed as if drafted jointly by the parties hereto and no presumption or burden of proof will arise favoring or disfavoring any party hereto because of the authorship of any provision of this Note. The words “include,” “includes,” and “including” will be deemed to be followed by “without limitation.” Pronouns in masculine, feminine, and neuter genders will be construed to include any other gender, and words in the singular form will be construed to include the plural and vice versa, unless the context otherwise requires. The words “this Note,” “herein,” “hereof,” “hereby,” “hereunder,” and words of similar import refer to this Note as a whole and not to any particular subdivision unless expressly so limited. The parties hereto intend that each representation, warranty, and covenant contained herein will have independent significance. If any party hereto has breached any representation, warranty, or covenant contained herein in any respect, the fact that there exists another representation, warranty or covenant relating to the same subject matter (regardless of the relative levels of specificity) which such party hereto has not breached will not detract from or mitigate the fact that such party hereto is in breach of the first representation, warranty, or covenant.

22. Mutual Drafting. This Note is the joint product of Payee and Maker and each provision hereof has been subject to the mutual consultation, negotiation and agreement of such parties and shall not be construed for or against any party hereto.

[Signature Page Follows]

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IN WITNESS WHEREOF, Maker, intending to be legally bound hereby, has caused this Note to be duly executed by the undersigned as of the day and year first above written.

[SIGNATURE PAGE TO PROMISSORY NOTE]

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