Cutting captives' heads off? Well, that's certainly something Japan has experience with.
...but that was a long time ago, and it doesn't lessen the hideousness of what happened to these two citizens. I hope they do take some type of meaningful action against ISIS but I doubt they will. At the end of the day this is something that gets people fired up for a week or so, that is useful politically, but the realities, risks, and expense of becoming meaningful engaged will, in my opinion, forestall anything kinetic.
The one exception I could see is if they somehow managed to send some of their SDF fighters to participate in the air campaign, which would not only be a meaningful political gesture but would also be pretty useful militarily.