Stylus is not used to write calligraphy or paint sumi-e. It is possible that this was shoved into a pile of other works, and humidity caused that ink was transferred onto another page leaving this pale mark. Since almost all ink types for calligraphy are disolvable in water, it could be the cause of those markings. They look like kanji, but it's really tough to read them. I don't think that those markings are integral part of the drawing itself.
@Akihiko Thank you! Although I think I have placed my signature slightly too low >.< and it damages the balance.