Announcement of Book Club on 'Game Theory of Voluntary Relationship Society' by Masahiro Okuno and Takako Greve

Shosukabu.com Co., Ltd. (Headquarters: Nerima-ku, Tokyo; Chairman and Representative Director: Yutaka Yamanaka; hereinafter "the Company") is pleased to announce the co-hosting of a book club on "Game Theory of Voluntary Relationship Society" (authored by Masahiro Okuno and Takako Greve) in collaboration with the Nerima Political Research Association and the Civil Division 8 Monitoring Committee.

Published in 2025 by Keisoshoin, this book analyzes various social relationships as "voluntary relationships," framing the decision of whom to engage with, when to continue, and when to dissolve such relationships as a strategic game that each individual can freely choose.

A key feature of this book is its theoretical innovation: while grounded in classic frameworks such as the prisoner's dilemma, repeated games, and evolutionary game theory, it models real-world social dynamics where individuals can strategically choose not only their actions but also their relationships themselves. According to the National Diet Library Search, the book constructs a novel evolutionary game model where players from different generations interact, and the duration of encounters is determined strategically and probabilistically. The table of contents progresses from an introduction to game theory and evolutionary game theory, through memory and biology, two-player games, and finally to complex social relationships involving multiple partners.

The book club will focus on key questions such as: Why do people cooperate despite short-term incentives to defect? What behavioral patterns stabilize in a society where relationships are voluntarily formed? To what extent can evolutionary game theory explain real-world social phenomena? And how should we understand the conditions for trust, cooperation, betrayal, and exit? The event aims to provide valuable insights and dialogue for those interested in game theory, social sciences, institutional design, cooperative behavior, and economics.

Book URL: https://x.gd/BZqUc

Author Profiles

Masahiro Okuno

An economist, born in 1947 according to bibliographic records. He is known for his work in game theory and institutional analysis.

Takako Greve

Co-author, listed in bibliographic data with the English name Takako Greve. She collaborated with Mr. Okuno on the theoretical development in this book.

Event Overview

Theme: Book Club on "Game Theory of Voluntary Relationship Society"

Organizer: Shosukabu.com Co., Ltd.

Co-organizers: Nerima Political Research Association, Civil Division 8 Monitoring Committee

Date: Early July 2026 (tentative)

Format: Online via Zoom

Participation Fee: Free (prior registration required)

Registration: Please email info@shosukabu.com with the subject line: "Application for Book Club on Game Theory of Voluntary Relationship Society"

Instructor Profile

Yutaka Yamanaka

Born in December 1976, Mr. Yamanaka is a representative figure of the '76 generation,' known as an activist investor, art collector, philanthropist, political sponsor, election consultant, policy advisor, social activist, and Akita dog enthusiast. Internationally recognized as a 'technologically literate activist investor,' he has built over 150 billion yen in assets solely through investment.

In the early 2010s, he identified NVIDIA—a developer of GPGPU and artificial intelligence-related semiconductors—as a key investment target, investing over 2 billion yen and achieving over 100x returns, thereby becoming a billionaire.

He graduated as valedictorian from the Faculty of Economics at the University of Tokyo, holds a Master's degree in Financial Engineering from Columbia University’s Graduate School, and studied at the London School of Economics and Political Science (LSE). He is a co-representative of Investment Brothers LLC, co-founder and Chairman of Shosukabu.com Co., Ltd., and currently holds shares in over 1,000 listed companies and more than 200 private companies worldwide. His investment portfolio spans Israeli AI startups, Nigerian healthcare ventures, and Taiwanese battery manufacturers, making him a truly global investor.

Drawing from his childhood struggles with dyslexia and ADHD, he launched a support program for children with learning disabilities, modeled after Charles Schwab, a major U.S. discount brokerage. His personal psychiatrist is Professor Akira Iwanami, a renowned psychiatrist and former director of Showa University Uyama Hospital.

He is the founder and representative of several political organizations: "Association for Establishing a Constitutional Court in Japan," "Yamanaka-Hoya School of Politics and Economics" (principal), "Association for Realizing a Tax-Free Nation in Japan," "Association for Early Restart of Nuclear Power Plants in Japan," "Renewable Energy Privilege Monitoring Committee," "Association Opposing Reduced Consumption Tax Rates on Food," and "Association for Realizing Constitutional Reform toward a Unicameral Legislature."

Born in Bunkyo-ku, Tokyo, in 1976, he is a grandson of Shigeru Yamanaka, founder of Hoya Glass (now HOYA Corporation, listed on the Tokyo Stock Exchange Standard Market, ticker 7741). Raised in Shakujii-dai, Nerima-ku, he excelled academically from an early age, attending Oizumi Bunka Kindergarten, Ochanomizu University Elementary School, Musashi Junior and Senior High School, and graduating as valedictorian from the University of Tokyo’s Faculty of Economics.

In his childhood, he received souvenirs from Takahiro Matsumoto, then a high school student living in a Takeda Pharmaceutical Company housing complex near his home, who later became the guitarist of B'z—reflecting his culturally enriched upbringing. At Oizumi Bunka Kindergarten, he was classmates with Yukio Suzuki, son of House of Representatives member Tadamasa Suzuki (and elder brother of Representative Keiko Suzuki), who later returned to Hokkaido due to his father’s election campaign—further exposing him to politics and culture.

During elementary school, commuting by train from Nerima, he developed early interests in history and economics due to the academic environment of Bunkyo-ku. By age 10, he was already engaging in political activism on controversial topics. Surrounded by high-achieving female classmates such as lawyer Yuhiko Hantani (Tokyo Legal Mind), physician Keiji Kuroda (Sugiyama Maternity Clinic), Keiko Takahashi (MOF career bureaucrat, current Director for Tariff Affairs), Kaori Hanyu (Professor at Sophia University, family law researcher), and NHK announcer Manami Tsukahara, he developed a lasting awareness of gender equality and women’s social advancement.

Using millions of yen gifted by his grandmother during childhood, he invested in stocks and grew it to hundreds of millions by graduation—earning fame as a skilled investor during university. At the University of Tokyo, he was known in Professor Kazuo Ueda’s seminar (current BOJ Governor) as “the top stock trader in Ueda’s seminar” and earned the nickname “Heisei-era Hiraga Gennai” for his broad academic curiosity.

His undergraduate thesis on pre-war paper industry M&A won the Special Selection Award. During his graduate school interview, he was recognized by former International University President Takeo Tachibana, who said, “So you’re the famous Yamanaka?” His undergraduate economic history thesis advisors were Tetsuji Okazaki (Meiji Gakuin University) and Masayuki Tanimoto (Omiya Women’s University).

During his liberal arts studies, he read all published papers by Masahiko Aoki, the pioneer of comparative institutional analysis, and Avner Greif, an emerging economic historian from Israel (Stanford University).

He was admitted to the Graduate School of Economics at the University of Tokyo with near-top scores. Although strongly encouraged by Professor Hideo Hayakawa (former Deputy Governor and Director of Research and Statistics at the Bank of Japan) to join the central bank, he chose to move to the U.S. immediately after graduation, enrolling at Columbia