So this is a closer look at how the driver becomes the chest at the heart of the combined mode.
There are obvious comparisons to the power master / breast master gimmick, but without this, the figure doesn’t work, it’s not just an additional add-on which presses down a button to allow transformation. The entire concept of the supporting fiction hinges on the fact that the driver is the sentient part of this fusion. The bikes are just power suits which they combine with.
It’s worth noting that the characters have their own internal power source, they are not reliant on any form of exterior energy. While the stories set in this universe will showcase mining as one of the few surviving industries, it will be more for materials and resources more-so than for energy / fossil fuels and survival.