The rapid aging of the population has become increasingly challenging for public healthcare systems. To ensure sustainability, governments must persuade their citizens to accept a larger burden, which is a difficult task. This study explored whether informing individuals of self-benefits from the healthcare system could be a solution. We first constructed a two-period overlapping generations model and hypothesized that doing so could facilitate political support for larger healthcare insurance contributions; however, this effect is reduced when people are concerned about fiscal sustainability due to a declining fertility rate. To test these hypotheses, we conducted an online survey experiment in Japan, in which the treatment group was informed of the benefits from the public healthcare system. We found that the treatment had no effect on average but augmented support for a larger burden among respondents who were unaware of fiscal unsustainability. Furthermore, this positive effect on optimistic respondents reduced once they were informed of the fiscal risks. Moreover, we analyzed the heterogeneity of the treatment effects depending on time and risk preferences.