Papers
Under review PDF
Throughout history, jurisdictional conflict among rival rulers has constrained oppression by enabling subjects to pursue mass exit—often to draw external intervention—as an alternative to directly confronting authority. I document this mechanism in Tokugawa Japan, where a feudal structure of domains with similar institutions but divergent tax burdens competed for subjects’ loyalty, creating an ideal setting to observe a competitive market for governance. Leveraging newly digitized village-level records of peasant resistance, I show that exposure to alternative authority—measured by the ratio of a village’s distance to its home-domain capital relative to the nearest foreign-domain capital—induced villages to opt for exit over confrontation. Moreover, domains facing more intense jurisdictional rivalry—measured by the average distance ratio across their villages—extracted lower taxes, accounting for alternative mechanisms. These findings highlight mass exit as an active means of popular constraint, surfacing a mechanism long overshadowed by scholarship’s emphasis on direct resistance and notions of passive exit.
Working paper
Political shocks are widely thought to spark social mobilization by converting private grievances into a shared experience. Yet why the same shock activates some constituencies and not others remains unclear. I adjudicate between two accounts: material conditions that alter the costs of mobilization, and ideological forces that shape how grievances are interpreted and made politically legible. Exploiting the May 15 Incident of 1932—a political assassination that marked a decisive turn toward fascist mobilization in Japan—as a natural experiment, I examine which populations responded to the shock. Using a difference-in-differences design with monthly prefecture-level data on right-wing organization density, I show that ideological determinants dominate: mobilization surged only where populations were already embedded in a preexisting ideological framework, while regions facing greater hardship or stronger organizational infrastructure remained dormant.
Working paper
While scholars broadly agree that feudal orders arose from the limitations of centralized state control, much less is known about the mechanisms through which this process began and unfolded—specifically, who fostered the fragmentation of state power and where it originated. I propose a theoretical framework identifying the conditions under which statebuilders deliberately hollow out their own administrative apparatus by privatizing extraction: granting fiscal immunities in exchange for a share of the returns. I evaluate the model’s implications using the case of early medieval Japan, where varying degrees of feudalization across regions can be systematically observed through estate commendations to the imperial court. Consistent with the theory, I find that estate commendation by emerging local warrior elites occurred most prominently in peripheral regions where central authority was weak but local administrative capacity remained strong.
Work in progress
Although agricultural surplus was vital for early state formation, it also exposed states to external threats. I claim that while surplus itself jeopardized states, the administrative capacity to generate it—specifically hydraulic management—promoted state persistence. Maintaining costly irrigation systems provided rulers with bargaining leverage over both external predators and internal subjects, deterred both invasions and defections, and thereby fostered stable territorial control. I illustrate this argument through a formal model and test it using global data of historical polities since 3400 BCE. Duration analysis shows that states with greater hydraulic dependence, measured by the potential yield gap between irrigated and rainfed farming, tended to endure longer without losing territories, while higher absolute yields accelerated territorial loss. The result was exclusively found in earlier periods, where developing hydraulic systems was more costly. Additionally, polities with greater hydraulic dependence tended to develop more complex social structures.
Work in progress
Social scientists have argued that conflict and military technological innovation fostered the formation of territorial states. While the literature has predominantly examined European history, Japan’s Warring-States Period offers a unique context to test this claim; the island country initially composed by more than 100 autonomous local powerholders (daimyo) was exposed to an exogenous shock of military innovation, an accidental importation of firearms in 1543, after which the fragmented society rapidly transformed into a centralized state under a singular authority. Using original grid-year datasets of battles, castles, and territorial changes, we show (preliminary, descriptive) results suggesting that the technological shock diminished defensive advantage and made economic power better translate into battleground success, thereby inducing small rulers to concede their autonomy.
Other Publications
Pacific Forum Issues & Insights, Vol.22, pp.31–49
Book chapter in 国際関係研究の方法 (University of Tokyo Press, 2021)
Talks
- Mobility and State Extraction in Early Modern Japan — MPSA 2025; JSQPS 2024 Summer
- When Freedom Backfires — JSQPS 2025 Summer
- Teppo Made Japan — Waseda University, 2023
- Empirical Model of Alliance Formation — Waseda University, 2022
- Threats and Assurances in Crisis Bargaining — MPSA 2021