Fabrics pre printed with sashiko designs (so you can skip the transfer step and get right to the good part, the stitching!) Pre printed designs will wash out when you are finished stitching. But please don't iron them before washing or the print may become set.
Some sashiko kits come with pre printed fabric and some have instruction for you to transfer the design to fabric. There are good reasons for choosing either. Pre printed is fast and easy, and if you need some handwork for travel it's perfect. On the other hand, learning to do the transfer for yourself will give you the freedom to choose your own fabrics and colors in future projects.