The drunken Toda wishes to show his gratitude to his boss Manabe-san, for not only going out to drink with him, but also for things like her making his lunches, while the two of them do the rounds together for work. But he doesn't notice or even try to find out her true feelings.

They miss the last train of the day, so they walk heading to Manabe-san's house and Toda notices her body smelling nice. He is sweating a lot. Once they collapse onto the sofa, it doesn't take long until her "downstairs" becomes soaking wet and ready for action. So he finally gets the message, and while he's guided by this revelation, they grow from drinking buddies to lovers.

(Source: DMM)