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Rainier Acquisition Corp. was the issuer in a beneficial-ownership report by Sio Capital Management, LLC, which reported 500,000 Units, or 5.67% of the class, as of September 30, 2026. Sio reported shared voting and dispositive power over the position. Each Unit consists of one Class A ordinary share and one-quarter of one redeemable warrant to acquire one Class A ordinary share. The reported percentage was based on 8,825,000 shares outstanding following the September 2, 2026 issuances.
Key Figures
Beneficial ownership:500,000 UnitsPercent of class:5.67%Shares outstanding:8,825,000 shares+2 more
5 metrics
Beneficial ownership500,000 UnitsSio Capital Management's reported amount as of September 30, 2026
Percent of class5.67%Sio Capital Management's reported beneficial ownership as of September 30, 2026
Shares outstanding8,825,000 sharesFollowing the September 2, 2026 issuances; basis stated for the reported ownership percentage
Class A ordinary shares per Unit1 shareEach Unit consists of one Class A ordinary share
Redeemable warrants per UnitOne-quarter of one warrantEach warrant is to acquire one Class A ordinary share
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
shared voting powerregulatory
"with shared voting power"
Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.
shared dispositive powerregulatory
"with shared dispositive power"
redeemable warrantfinancial
"one-quarter of one redeemable warrant"
A redeemable warrant is a financial tool that gives its holder the right to buy shares of a company at a fixed price within a certain period. If the holder chooses to do so, the company can buy back or cancel the warrant before it expires, often to encourage investment or manage share issuance. For investors, it provides an option to potentially buy shares at a favorable price while offering some flexibility for the issuing company.
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
How many RNAQ Units did Sio Capital Management report owning?
Sio Capital Management reported beneficial ownership of 500,000 Units, representing 5.67% of the class as of September 30, 2026. It reported shared voting and dispositive power over the position.
What does one RNAQ Unit include?
Each Unit consists of one Class A ordinary share and one-quarter of one redeemable warrant to acquire one Class A ordinary share.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Rainier Acquisition Corporation
(Name of Issuer)
Units, each consisting of one Class A ordinary share and one-quarter of one redeemable warrant to acquire one Class A ordinary share
(Title of Class of Securities)
G73591110
(CUSIP Number)
09/30/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
G73591110
1
Names of Reporting Persons
Sio Capital Management, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
500,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
500,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
500,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.67 %
12
Type of Reporting Person (See Instructions)
IA
Comment for Type of Reporting Person: 1 As of September 30, 2026, Sio Capital Management, LLC beneficially owned 500,000 Units with shared voting power and shared dispositive power.
2 Based upon 8,825,000 shares outstanding following the September 2, 2026, issuances, calculated from the disclosures in the Issuer's Form 8-K filed September 3, 2026.
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Rainier Acquisition Corporation
(b)
Address of issuer's principal executive offices:
1 Penn Plaza, 48th Floor, New York, NY 10119
Item 2.
(a)
Name of person filing:
This Statement is filed on behalf of Sio Capital Management, LLC (the "Reporting Person" or "Sio")
Sio is a registered investment adviser to certain affiliated funds that directly hold the shares of Common Stock to which this statement relates for the benefit of their respective investors, and in such capacity Sio has voting and dispositive power over such shares.
(b)
Address or principal business office or, if none, residence:
600 Third Avenue, 2nd Floor
New York, New York 10016
(c)
Citizenship:
Sio is a Delaware limited liability company.
(d)
Title of class of securities:
Units, each consisting of one Class A ordinary share and one-quarter of one redeemable warrant to acquire one Class A ordinary share
(e)
CUSIP Number(s):
G73591110
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
500,000
(b)
Percent of class:
5.67 %
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
0
(ii) Shared power to vote or to direct the vote:
500,000 - Refer to footnote 3
3 Sio and Sio GP, LLC (the "GP") act as investment advisor and general partner, respectively, to various clients that are the record owners of the Common Stock reported on this Schedule 13G. Because Sio's investment discretion with respect to such clients is subject to oversight by the GP, the GP may be deemed to be the beneficial owner of the Common Stock of the Issuer owned by such clients. In addition, both Sio and the GP are controlled by Michael Castor. As such, he may be deemed to control the voting and dispositive decisions with respect to, and therefore be the beneficial owner of, the shares of Common Stock reported on this Schedule 13G. Neither the filing of this Schedule 13G nor any of its contents shall be deemed to constitute an admission by the GP or Michael Castor that such person is the beneficial owner of any of the equity securities referred to herein for purposes of Section 13(d) of the Exchange Act, or for any other purpose, and such beneficial ownership is expressly disclaimed.
(iii) Sole power to dispose or to direct the disposition of:
0
(iv) Shared power to dispose or to direct the disposition of:
500,000 - Refer to footnote 3
3 Sio and Sio GP, LLC (the "GP") act as investment advisor and general partner, respectively, to various clients that are the record owners of the Common Stock reported on this Schedule 13G. Because Sio's investment discretion with respect to such clients is subject to oversight by the GP, the GP may be deemed to be the beneficial owner of the Common Stock of the Issuer owned by such clients. In addition, both Sio and the GP are controlled by Michael Castor. As such, he may be deemed to control the voting and dispositive decisions with respect to, and therefore be the beneficial owner of, the shares of Common Stock reported on this Schedule 13G. Neither the filing of this Schedule 13G nor any of its contents shall be deemed to constitute an admission by the GP or Michael Castor that such person is the beneficial owner of any of the equity securities referred to herein for purposes of Section 13(d) of the Exchange Act, or for any other purpose, and such beneficial ownership is expressly disclaimed.
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
Not Applicable
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
Not Applicable
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
