Complex sentence: His Shōkanjū wears a school uniform and wields a bokken but during the ESB field error, his being wasnt affected, but multiplied enough to literally flow out of the school itself.
Split into simpler sentences: His Shōkanjū wears a school uniform and wields a bokken. During the ESB field error, his Shōkanjū wasn't affected, but it multiplied enough to literally flow out of the school itself.