Behavioral targeting (BT) is an important function for a company to reach a wide range of potential users. Trans-domain BT which targets potential users of one (source) domain (e.g. E-Commerce) who lie in another (target) domain (e.g. Ad Network) is a promising method to expand the range. However, it is difficult for trans-domain BT to keep its targeting quality high in case when ID linkage across domains is limited. To realize high quality trans-domain BT with limited ID linkage, we propose a method to cross-connect private touchpoints to users in each domain, which we call Virtual Touch-Point (VTP). Here, we utilize transfer learning to acquire knowledge to tie two domains. We made a VTP prototype by implementing typical transfer learning algorithms and evaluated its effectiveness using real-world data of two domains: (source) E-Commerce → (target) Ad Network.