Most Millennium Godzilla films (1999-2004) are standalone reboots ignoring all previous films except the 1954 original. Tokyo SOS is the exception. It directly follows Godzilla Against Mechagodzilla . You need to know that Akane Yashiro (the female pilot) is traumatized, and that Kiryu (Mechagodzilla) has a soul—the bones of the original 1954 Godzilla.
: Navigate to the Internet Archive and search specifically for "Godzilla Tokyo SOS" to find the most current uploads. Note that some items may occasionally be removed due to licensing restrictions. godzilla tokyo sos internet archive