AbstractHighly frustrated spin systems such as the kagome lattice are a treasure trove of new quantum states with large entanglements. Herein, we study the spin-$$\frac{1}{2}$$
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Heisenberg model on a kagome-strip chain, which is a one-dimensional kagome lattice, using the density matrix renormalization group method. Calculating the central charge and entanglement spectrum for the kagome-strip chain, we find a gapless spin liquid state with doubly degenerate entanglement spectra in a 1/5 magnetization plateau. We also obtain a gapless low-lying continuum in the dynamic spin structure calculated using the dynamical density matrix renormalization group method. We then propose a resonating dimer–monomer liquid state that meets these features.