18+ Hiyoko Strike! Houmatsu no Yume

The usual classroom. The usual boring lesson. Shin stared outside blankly and then suddenly a girl appeared… outside the 2nd floor window! She jumped in from the window and introduced herself as Utakata. Everything else was just as illogical: taking her clothes off while standing on the desk, sticking her finger up his nose, and having things that look like animal ears and tail. His head hurt from all this, but at the same time he was also a bit excited since the world that he knew became more vivid.

(Source: Hau~ Omochikaeri!)