On March 12th, I photographed Tokyu 5050 Series 4115F set, which couples two "Q SEAT" longitudinal/transverse rotatable seat carriages.
4115F set used to be in service as an 8-carriage 5169F set. In 2023, the two "Q SEAT" carriages are added to the set between the third and fourth carriages.
The "Q SEAT" carriages have been in regular service in the longitudinal since 2022 because Toyoko Line plans to start the seat reservation service within a few years.
The "Q SEAT" carriages on Toyoko Line have a red-coloured livery, but it looks darker than the line on the other carriages.
The sets with "Q SEAT" carriages differ in the order of the carriages from the other 10-carriage (4101F - 4111F sets) from a mechanical aspect. In the case of all longitudinal seating sets, the sixth carriage from Shibuya is an independently motorised carriage. However, the fifth carriage of those with "Q SEAT" does.