Upvote:5
Check the website of your specific airline (I it's assume ANA or JAL). Most airlines will accept whatever you want to check in as long as it's within weight and size guidelines and poses no danger. For something flimsy they will waive any type of responsibility and might make you sign a waiver if you insist on checking it it at your own risk.
In general, regular duffle bags are fine for check in. But if your bag is unusual in some way, it's your problem if it gets destroyed and/or contents are lost. The airline will not take responsibility.