Touge Oni: Primal Gods in Ancient Times, Vol. 3 — Kenji Tsurubuchi

As Miyo is fixed to be a permanent part of the group on their journey to Mount Katsuragi, En properly assumes the role of master and teacher, beginning with the basics of reading and writing. The unfamiliar characters are a struggle, but when another divine instrument forces an unexpected detour, Miyo's mastery of them -- combined with a bold strategy -- may be her only hope of rejoining the others!