The Misfit of Demon King Academy, Vol. 6 (light novel)

Although he thought his reincarnation was complete, Anos soon realizes he can't recall fragments of his past. With the help of Arcana and her stolen power, he dives into a dream, where he finds a younger and far less skilled version of his current self fighting bravely to protect his beloved sister. Whether by coincidence or fate, that sister's name is Arcana-the same name as the Selection God fighting alongside him. To determine the truth of these memories and to learn more about the underground world, Anos takes the students of the Demon King Academy on a trip to Jiordal, Kingdom of the Divine Dragon, where the ruler declares Arcana the reincarnation of the Militia, Goddess of Creation. So who is Arcana? Is she the Goddess of Creation, or is she his sister? The truth is yet to be seen...