The first few chapters were rough to follow because they skipped over so much time to set up the main plot but now that we're arriving at the first mystery we don't really understand anyone and as the person above said the timeline is being presented poorly.
So last chapter showed an explosion and said the princess was gone. This chapter ignores that, sets up the principles of a standard locked room mystery, then sets off an explosion in the main building, not the locked room, and says the victim is missing. I didn't even know she left the chapel. Then they say they need to wait for explosives to blow the doors open because magic is too complicated to break doors. And finally they name drop a "Great Detective" and I think that's kind of weird that profession already exists before the MC like it's not exactly a common Isekai trope for medieval worlds to have detectives. It's not a big deal but like isn't the cast already kind of bloated for chapter 6? Do we need to introduce an existing detective?