Some days ago I could photograph of a semi express train bound for Motomachi-chukagai by Tokyu 5050 Series.
There're just 1 operation on the weekday morning and 4 on the holiday evening of semi express trains for Motomachi-chukagai on Seibu Ikebukuro Line.
The weekday one from Kotesashi departing at 8:42 AM by Tokyo Metro unit changes to express on Fukutoshin Line and to limited express on Tokyu Toyoko Line. One of 4 holiday operations from Tokorozawa departing at 8:25 PM by Seibu unit does to express on Fukutoshin and Toyoko Lines. The other 3, 7:49 PM from Kotesashi, 8:55PM from Tokorozawa, and 9:25 PM from Tokorozawa does to local on Fukutoshi and Toyoko Lines.