Akashic Records Bastard Magical Instructor GN Vol 16

Sisti is a young magic-user in training who attends prestigious magical academy where she hopes to be trained by the best of the best. However, when her instructor suddenly retires, his replacement is anything but what Sisti had hoped for-lazy, incompetent, and always late! Can Sisti still learn magic and unravel the mystery of Sky Castle with such a terrible teacher to lead her?