We will talk about restricting the domain of a Hilbert modular form in the Kohnen plus space to the diagonal. This technique was initially brought up by Siegel in considering the case of integral weight. It turns out that if we consider the Kohnen plus space upon real quadratic fields with certain condition, the image will be contained in the plus space of odd weight which is isomorphic to the space of Hermitian modular forms and was introduced by Kojima. We will give an inspection in terms of Weil representation and as a result derive some linear relations between the L-values and arithmetic functions.