Magnetic-Flux Tuning of Second Harmonic Content in Intrinsic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>CsV</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:m

The current phase relation (CPR) determines the electromagnetic response of Josephson junctions in superconducting circuits. It is sensitive to the weak link materials and interface quality. In this work, we report the intrinsic Josephson effect originating from domains in the single-crystal kagome superconductor CsV_{3}Sb_{5}, where no artificial weak links were introduced. By tuning the magnetic flux, we observe the Josephson diode effect and clear half-integer Shapiro steps. The quantitative analysis reveals a significantly enhanced second harmonic content in the CPR, exceeding the ballistic limit of a single Andreev Josephson junction. Such a pronounced second harmonic component is attributed to the nonuniformity of the current distribution and the nonsinusoidal CPR in highly transparent intrinsic Josephson junctions. The intrinsic Josephson junction formed at the domain wall shows the potential application for superconducting quantum technologies.