By personal ami,source
train fact
Speaking of Ami, ami means friend in French , which start with letter F, which also the F-liner does.
F-liner is a express train service operated by 5 private train companies, providing express train service between Yokohama and Tokyo subcenter (Fukutoshin).
With F liner, you can save interchange time..
... and no additional fee!!!(because the trains are literally commuting train running express service, expect no fancy seats)
F-liner run by Tokyo Metro 10000 series
F-liner run by Tobu 9000 series
Not to be mixed up with NYC Metro F line
Hmm not by me