Satou was heading on his way to a tour late at night via night bus.

The seat beside him was vacant because his friend cancelled on him at the last minute, and so he found himself giving the vacant seat to a girl who was having trouble.
Her name is Aika, and she's a sociable and very charming college student who's got a voluptuous body.

While everyone else inside the bus was sleeping, Satou got horny, and failing to hold himself back, his hand began to wander over to the vulnerable Aika who was fast asleep beside him...

(Source: DMM)