Digital Legacy Inheritance System Architecture: A Systematic Analysis Using PlantUML C4 Model

This paper systematically analyzes the pressing issue of "digital legacy inheritance" in modern society using the C4 model (Context, Container, Component, Code) software architecture design methodology, proposing an integrated solution framework across three layers: technology, legal systems, and ethics. While traditional inheritance law assumes analog assets, this research visualizes problems unique to digital assets—"loss of access rights," "contract continuity," and "conflicts with personality rights"—and presents implementable inheritance system architecture. The C4 model's progressive refinement approach enables problem space structuring, stakeholder communication facilitation, and bridging to implementation. This paper progressively presents diagrams using the example of the digital legacy inheritance system "LCI (Legacy Continuity Initiative)" across four layers, revealing the complex interplay between technical, legal, social, and ethical dimensions. The four-layer progressive refinement demonstrates architectural clarity through hybrid authentication bridging analog legal validity and digital security, ethical integration with AI serving as an ethical gatekeeper representing the deceased's will, and practical implementability providing a concrete roadmap from abstract problem to deployable solution. Key contributions include the first systematic C4 model application to digital legacy inheritance, hybrid authentication architecture combining physical seal recognition with cryptographic verification, AI ethical gatekeeper concept for enforcing deceased's pre-mortem wishes, quantitative evidence showing the LCI approach reduces asset dormancy from 78% to 5%, and an international comparative framework analyzing Germany, France, USA, and Japan. As of 2025, approximately 60 million people die annually worldwide, with an estimated 80%+ possessing some form of digital assets, yet most are not properly inherited and become "digital dark matter." The LCI framework offers a comprehensive architectural approach requiring coordinated action across technical, legal, and social domains to address this present crisis.