I feel like I'm neglecting Aiba since I've yet to watch any of Mikeneko Holmes (sorry Aiba!!), but wow, KagiHeya is AMAZING. :D It haven't been this wrapped up in a drama for ages now, and it has mystery with mind puzzles, one of my favourite genres alongside comedy (so it would seem like Mikkeneko Holmes would suit my tastes too, haha).
The music is quirky, easy to catch on and very unique in some instances, it really strikes a good balance with Enomoto's equally quirky character. :3 And they've also been incredibly detailed in how they subtely change the opening credits for every episode, it's fun looking for the clues, haha.
More for my own reference than anything:
Episode 1
The syringe that gets flung onto the door, and the fly the comes in near the end of it. (This one was pretty obvious)
Episode 2
The confetti that flew out when Enomoto opened the door, but upon closer inspection, the combined gas law is present behind him inside the room. =0 I thought that was pretty neat.
Episode 3
Chain on the door, and the blue numbers/letters that linger for a little while when Serizawa reaches for the key. I felt compelled to check the other episodes again to make sure it was episode specific (because I haven't watched this episode beyond the opening credits yet at this point in time XD).
Now that I know the answers are shown prior to any proper investigation, I'll be keeping a closer eye on it. :") Ahh, KegiHeya is so gooood!! <3