Fact: The Keio Inokashira line connects Shibuya and Kichijōji, which are some high economy development area. (Idk how to describe). It is noticeable for their colorful livery.
Moreover, due to some history reasons, it is not connected to the Keio Main line as the track gauge is different. You can distinguish Keio Main line trains and Keio Inokashira line trains by their livery: Usually, Keio Main line trains use white livery.
And their Semi Special Express has canceled.
Gorō Inogashira in Kodoku no Gourmet
Sentai Trains.