Summary: We prove the arithmetic inner product formula conjectured in the first paper of this series for \(n = 1\), that is, for the group \(U(1,1)_F\) unconditionally [Algebra Number Theory 5, No. 7, 923–1000 (2011; Zbl 1258.11061)]. The formula relates central \(L\)-derivatives of weight-2 holomorphic cuspidal automorphic representations of \(U(1,1)_F\) with \(\varepsilon\)-factor \(-1\) with the Néron-Tate height pairing of special cycles on Shimura curves of unitary groups. In particular, we treat all kinds of ramification in a uniform way. This generalizes the arithmetic inner product formula obtained by Kudla, Rapoport, and Yang, which holds for certain cusp eigenforms of \(\text{PGL}(2)_{\mathbb Q}\) of square-free level.