  Battle with COVID-19 turned out to be a marathon, not a sprint, and
behavioral adjustments have been unavoidable to stay viable. In this paper, we
employ a data-centric approach to investigate individual mobility adaptations
and mask-wearing in Seoul, South Korea. We first identify six epidemic phases
and two waves based on COVID-19 case count and its geospatial dispersion. The
phase-specific linear models reveal the strong, self-driven mobility reductions
in the first escalation and peak with a common focus on public transit use and
less-essential weekend/afternoon trips. However, comparable reduction was not
present in the second wave, as the shifted focus from mobility to mask-wearing
was evident. Although no lockdowns and gentle nudge to wear mask seemed
counter-intuitive, simple and persistent communication on personal safety has
been effective and sustainable to induce cooperative behavioral adaptations.
Our phase-specific analyses and interpretation highlight the importance of
targeted response consistent with the fluctuating epidemic risk.
