Really just a re-branding of existing services using the Fukutoshin line for through running, but intended to be easier to understand for passengers, given the different train designations attached to a train as it passes through each railway. Began running under this monicker from the March 26 timetable revision.
http://www.tobu.co.jp/file/pdf/3d2881ee48143e73f17131401fbfdbfd/151218-4.pdf?date=20151218192334
*the "F" stands for "fast", "five", and "Fukutoshin"