Monster Girl Encyclopedia Stories: Diary of the Age of Monster Love

Diary of the Age of Monster Love is a 4-story novella containing brief descriptions of encounters with a Slime, a Holstaur, an Anubis, and a Succubus. This material has yet to be translated into English.

Canonity
Kenkou Cross is known to wholeheartedly encourage MGE fan writing. These books appear to be fanfic stories by another author (named ストレンジ, 'Strange'), in this case) which Kenkou providing endorsement, artwork, and publication under the Monster Girl Encyclopedia name.

However, this book was descripted to be set in "if world" (if世界), indicate that it's alternate setting to the official one.