After-School Bitchcraft Vol. 2 (manga)

While Renji continues to train Ririka, he's visited by none other than Berta Mathers, his former pupil and a member of the Sorcerers' Association! She's come to keep an eye on him, and when she finds him dabbling in forbidden magic...she's more than ready to teach him a thing or two. But they've got bigger problems, as one of Berta's colleagues catches Ririka alone and attacks her! Will Renji and Berta make it in time to save her?