I upload a raw scan of tinkle's doujin for reference. For a to-be-stitched tinkle scan, you need to obtain a raw of such quality, otherwise it's completely a waste of time editing/stitching tinkle's pic.
1. lossess bmp/png etc. Never use document mode, scan a pdf and convert.
2. use auto exposure, or completely close any color adjustment. I chose auto exposure to save some time of editing color.
3. align the pic according the crease, don't align with other edges, you will crop more in this case. It's the crease which need to be fixed.
4. In case you really need a help, don't upload the raw here, upload it to somewhere else and ask for help in the forum.

why not use paint, scooch it over a hair?