After missing the last train home, Mukai reluctantly accepts an invitation to spend the night at his boss Mako's apartment. Although he already has a girlfriend, the unexpected overnight stay gradually erodes the professional boundaries between them. As lingering emotions and unspoken desires surface, what begins as a simple act of kindness develops into a complicated relationship that forces both of them to confront temptation, guilt, and the consequences of crossing a line that should never have been crossed.