Gakusei Shoujo

Gakusei Shoujo (楽聖少女) is a light novel series by Hikaru Sugii with illustrations by Mel Kishida.

Plot
The main character is taken back in time to the 1800s by a devil under the pact made by Johann Wolfgang von Goethe. According to the devil, Goethe's request is for his body to be replaced by MC's, and then his soul to be implanted into MC's body and to slowly take over. As such, MC shares memory and knowledge of Goethe. The devil will claim Goethe's soul (which is now MC's soul) the moment MC declares he wishes time to stop due a state of ultimate bliss.