I found this volume very fun and enjoyed the introduced characters. I just think that now that we've reached volume 5, it becomes increasingly obvious that everything will go right for the main cast. I miss a sense of real danger a little, but as I've been saying since the first review, I think this LN is not something for you if you're looking for a complex and mysterious thriller story.
That said, the characters are truly the best part of Spy Classroom. Even though they are stereotypes of characters you'll find in anime/manga/LN, they are so well-crafted and that's really cool.