Let \(\mathbf{k}=(k_1,\ldots, k_r)\in \mathbb{N}^r\) with \(k_r\geq 2\). The multiple zeta value (MZVs) of index \(\mathbf{k}\) is defined by \[ \zeta(\mathbf{k})=\sum_{0<m_1<\cdots<m_r}\frac{1}{m_1^{k_1}m_2^{k_2}\cdots m_r^{k_r}}. \] Let \(\mathbf{k}^\star\) be the dual index of \(\mathbf{k}\). An immediate consequence of the iterated integral expression of multiple zeta values (MZVs) is the duality relation \[ \zeta(\mathbf{k})=\zeta(\mathbf{k}^\star). \] S. Seki and the author [Int. J. Number Theory 15, No. 6, 1261–1265 (2019; Zbl 1443.11183)] gave a new method of proving the duality, which used certain multiple sums called the connected sums and made no use of the integrals. An advantage of this method is that it can be directly generalized to obtain a \(q\)-analogue. In the present paper under review, the author applies it to multiple polylogarithms (MPL) \[ \mathrm{Li}_k(z_1,\cdots, z_r)=\sum_{0<m_1<\cdots<m_r} \frac{z_1^{m_1}z_2^{m_2-m_1}\cdots z_r^{m_r-m_{r-1}}}{m_1^{k_1}m_2^{k_2}\ldots m_r^{k_r}} \] and their \(q\)-analogues.