So I'm going to post two pictures. Both are the AIS (Automatic Identification System) shots of the area in question. Both have the past track of the ACX Crystal (The ship they hit) on them, but every other little colored arrow on those pics is a vessel of some kind transiting in or out of Tokyo Bay. Scales are on the lower left. AIS is basically a commercial transponder system for ships. Also remember that there are little fishing and pleasure boats out there not running AIS. And most of them don't speak English as a first language when you get them on the radio.
Given the traffic I'd be shocked if they were running dark or EMCON. The Fitzgerald was transiting a shipping lane south outbound for sea. The main route southwest from Tokyo Bay is between Oshima and Shimoda, so it's likely their course was in there somewhere and generally southwest.
If that's the case it was a crossing situation and the Fitzgerald was obligated to give way to the Crystal.
The AIS track looks like the Crystal did a sharp turn to starboard about 0133 local and slowed down. She then continued on roughly her previous course for 10-ish miles, turned around, returned to the site of the sharp turn and loitered there for a while, then proceeded to Tokyo. If I had to guess the first turn was the collision, then she straightened out and slowed down while she did Damage control, and accounted for all her crew, then when it was safe she returned to Fitzgerald see if she could render aid, and after that headed for port. Obviously I'm interpreting from only one data source, but that fits the known data.
US Navy ships don't run AIS, for obvious reasons, but that's what the Crystal's track looks like.
AIS normally integrates with your RADAR and Electronic charts and puts a little triangle on it for you. Folks get too dependent on that and forget that while triangle on the screen means there IS a boat, no triangle doesn't mean there ISN'T. I suspect we'll find that the Fitzgerald was on their RADAR, but they didn't think it was a real target, because AIS wasn't tagging it, and that confusion led to the Crystal not taking action until too late. Fitzgerald, however knew damn good and well she didn't have AIS on, was the give way vessel, and had better sensors then the Crystal. There's no real excuse for her not leaving quite a bit of room.
For perspective we (US Military vessels) normally go for CPA's measured in miles, or at least thousands of yards.