@Lucci Jiken means "case" like a detective case, and Jaken is just grammar with an accent from where the characters are from (around Hiroshima I think). It's added to the end as sort of a rhyme.
@meidunk
Dagashi Kashi is bad, but at least it's informative if you're able to care about the history of Japanese candy. This doesn't provide anything at all.
This is pretty funny 😂
I thought with a mystery tag this is going to be a serious series, but actually it's quite the opposite.
Also, the senpai kinda looks like Senjougahara. 😆