SY Meta Diary -- Using Cluster, the Japanese Metaverse Platform That Gave Birth to Virtual Shibuya Halloween: Recently Japan government Web3 industry promotion without hesitation is attracting global attention. Among Japanese metaverse platforms having the most influence in Japan, this report reviews Cluster app. The Cluster app already exceeded 1 million downloads by May 2024, with cumulative visitors exceeding 8 million. Cluster was created by a Japanese company Cluster Inc. -- a virtual space experience application that started in 2020. Virtual Shibuya Halloween: Cluster is best known internationally for hosting Virtual Shibuya Halloween, a large-scale virtual event recreating the famous Shibuya Halloween street party as a metaverse experience; the 2020 virtual event (held during COVID when physical gatherings were prohibited) demonstrated that metaverse can create genuine cultural event experiences at scale; subsequent years continued the event even after physical restrictions lifted, suggesting genuine user preference for the virtual format alongside physical events. Japan metaverse policy context: Japan government Web3 and metaverse promotion reflects strategic positioning -- Japan wants to be the global leader in digital content and cultural experiences exported through metaverse platforms; Cluster success is cited as evidence that Japan metaverse ecosystem can produce globally significant platforms.