Now, I always found "Hello Kitty" rather unsettling (the cat has no mouth!), but I never associated it with radical jihadism.
As Britain's The Independent commented in one of the many reports on this video:
Wearing combat uniform, with gun holsters strapped on, the commander seems unlikely to have chosen a pink Hello Kitty notebook to enhance his image.
The pink pad could have arrived in aid convoys sent to war-torn Syria or in charity packages, or maybe he is a genuine fan of the Japanese cartoon cat.