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