18+ Seiju no Kuni no Kinjutsukai

One day, Kurohiko Sagara, who was fed up with everything, is surrounded by a bright light and loses consciousness. When he wakes up, he finds himself in a different world with a humongous tree! In addition, for some reason he can easily read the "forbidden spells" that nobody has been able to read thus far, and because of that he ends up enrolling in the academy that trains "Sacred Tree Knights."

(Source: Gimme Manga!)