here is a list of ways to get seal scrolls each week

matsuri challenge - 1.5 seal scrolls - monday/friday
sage battlefield - 1 seal scroll for top 3 .5 seal scroll for winning team - sunday/tuesday/thursday
chase missions - 1 per weekend gives seal scroll
weekly miniclient login - .5 per week

total possible is 9 per week before war packs which can give 5-10 more

you c*so get them from events and lucky drops from survival trial