In another bout of thinking too deeply about this manga... Department store bicycles. Bikes are shipped to stores partially assembled and someone needs to finish building them before they get put on display. But because department stores run on hiring people for low wages, you don't find the best bike mechanics. The bikes often have build errors, some of them serious safety errors like undertightened stems or wack shifting that will bind up the chain.
So who built the bikes in the home center? I know the home center magically replaces things taken off the shelves. But does it replace an expertly built bike, or a poorly built bike?