Using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>B</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>K</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:mi>ν</mml:mi> <mml:mover acce

We introduce a model-independent framework to reinterpret Belle II results using only public data, analytically reconstructing the mapping between true and reconstructed kinematic variables within the statistically dominant Inclusive Tagging Analysis. This enables rare-decay measurements to probe light invisible particles—such as the QCD axion or axionlike particles, collectively denoted by <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mi>a</a:mi> </a:math> —without relying on internal simulations. Applying the method to <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:msup> <b:mi>B</b:mi> <b:mo>+</b:mo> </b:msup> <b:mo>→</b:mo> <b:msup> <b:mi>K</b:mi> <b:mo>+</b:mo> </b:msup> <b:mi>ν</b:mi> <b:mover accent="true"> <b:mi>ν</b:mi> <b:mo>¯</b:mo> </b:mover> </b:mrow> </b:math> yields the strongest bound on the branching fraction for <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:msup> <d:mi>B</d:mi> <d:mo>+</d:mo> </d:msup> <d:mo>→</d:mo> <d:msup> <d:mi>K</d:mi> <d:mo>+</d:mo> </d:msup> <d:mi>a</d:mi> </d:mrow> </d:math> , improving existing limits by about a factor of 9 and constraining the axion's fundamental flavor-changing coupling to <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mi>b</e:mi> </e:math> and <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mi>s</f:mi> </f:math> quarks. The approach establishes <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mrow> <g:msup> <g:mi>B</g:mi> <g:mo>+</g:mo> </g:msup> <g:mo>→</g:mo> <g:msup> <g:mi>K</g:mi> <g:mo>+</g:mo> </g:msup> <g:mi>ν</g:mi> <g:mover accent="true"> <g:mi>ν</g:mi> <g:mo>¯</g:mo> </g:mover> </g:mrow> </g:math> as a dual probe—simultaneously testing short-distance new physics and light invisible states, the two probes working independently to an excellent approximation—and provides a general strategy for model-independent reinterpretation of collider data.