First of all, I LOVE this journal, the flexible cover is very useful and there is a ribbon for a bookmark. The pages are also very thick (about 120gsm!!!) so not much will bleed through the pages. Overall, I recommend this product to any bullet journal users, this will improve your life! I also got the dotted journal so it is very useful.
I have all of these art mediums which I use and thus far none of them have bled through the paper, from Muji pens to watercolour, alcohol markers and water-based markers.