Recent information systems have become large and complex by interacting with each other via networks. This makes assuring dependability of systems much more difficult than ever before. For this problem, we observe that requirement elicitation and risk analysis methods should be tightly connected with assurance methods. Furthermore, requirements should be ensured also in operation in such open environment where several interdependency may exist. This paper describes our initial research result and preliminary implementation toward consensus building and in-operation assurance for service dependability. We propose a process cycle for consensus building among stakeholders with assurance cases. We extend conventional assurance cases for ensuring that stakeholders’ requirements are satisfied during operation. The extended assurance case is called D-Case[16]. We also describe how D-Case is used for in-operation assurance.